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Press & Stamping Force Calculator
In short: punching force is F = perimeter × thickness × shear strength; the press tonnage you specify adds a stripping allowance and a safety factor on top. Enter the cut perimeter, thickness, and shear strength below (or a tensile strength to estimate it) and this tool returns the cut force, stripping force, and total press force in kN and tonnes — with a bending mode for press-brake work.
Punching force and press tonnage
Fcut = P · T · τ · Fstrip = k·Fcut · Ftotal = (Fcut + Fstrip)·safety
Total press force
87.08 kN · 8.88 t
Size the press above the total force; shear strength from a data sheet gives the best result.
What this calculator computes
This tool works out the force a press needs to punch, blank, or shear sheet metal, and turns it into the press tonnage you actually specify. From the perimeter of the cut, the material thickness, and the material’s shear strength it computes the cutting force, then adds a stripping allowance to pull the punch back out and a safety factor for real-world variation, giving the total press force in kilonewtons and tonnes, or pounds and US tons. It also estimates shear strength from tensile strength when you do not have it, models the force reduction from a shear-angled punch, handles several features punched in one stroke, and includes a separate bending-force mode for press-brake work.
The reason this matters is that specifying the press is the decisive step in planning a stamping or cutting operation. Too small a press cannot make the part, or stalls and damages the tool; too large a press wastes capital and floor space and may be less controllable. The cutting force itself is only the theoretical minimum — the real load includes the stripping force and a margin for tool wear, clearance changes, and material variation — so the number that sizes the press is always larger than the textbook cut force. Getting that total right, and knowing the levers that change it, is the heart of press selection and tool design.
What sets this calculator apart is that it gives the whole picture, not just the raw punch force. It reports the cut force, the stripping force, and the total press tonnage together; derives shear strength from tensile strength when needed; models a shear angle and multiple features so you can see how to fit a job on a smaller press; and covers both cutting and bending. It carries a shear-strength reference by material, plots force against thickness, and runs entirely in your browser with nothing stored.
How to use this calculator, step by step
Begin by choosing the operation and units. The cutting mode covers punching, blanking, and shearing; the bending mode covers a press-brake air bend. Choose metric, with millimetres and newtons per square millimetre, or imperial, with inches and psi. The input fields change with the operation, so you are only asked for what that mode needs, and the material thickness and an optional tensile strength are shared by both.
For a cutting operation, enter the cut perimeter, the thickness, and the shear strength. The perimeter is the total length of the cut edge — for a round hole it is π times the diameter, so a 20 mm hole has a perimeter of about 62.8 mm, and for a profile it is the length of the whole outline.
If you do not know the shear strength, enter the tensile strength instead and leave the shear field blank; the calculator estimates shear as about 0.7 times tensile. Then set the number of features punched in the same stroke, any shear-angle reduction, and the stripping percentage.
The calculator opens on a worked example — a 20 mm hole in 3 mm mild steel at 350 N/mm², 10 percent stripping, and a 1.2 safety factor — giving a total press force of about 87 kN, or 8.9 tonnes.
Read the result panel, which leads with the total press force in kilonewtons and tonnes, then lists the total force in newtons, the raw cut or punch force, the stripping force, and the shear strength used (flagged if it was derived from tensile). The chart plots how the cut force grows with material thickness, which makes the strong effect of thickness visible. In bending mode, enter the bend length and the die opening, and the tool returns the bending force. You can download or share the result, all locally.
The punching force formula
The cutting force in punching, blanking, and shearing all come from the same idea: the punch has to shear the material along the cut line, and the force is the shear stress the material can take multiplied by the area being sheared. That sheared area is the perimeter of the cut times the thickness of the sheet — imagine unrolling the cut edge into a thin rectangle whose length is the perimeter and whose height is the thickness. Multiplying that area by the shear strength gives the force: F = perimeter × thickness × shear strength. It is a compact formula, but each term carries real weight in practice.
The perimeter is set by the shape being cut, not its area. A round hole has a perimeter of π times its diameter; a rectangular slot has a perimeter of twice its length plus twice its width; a complex blank has the length of its whole outline.
This is why a long thin slot can take as much force as a much larger round hole — force follows the cut length, not the enclosed area. The thickness enters linearly, so doubling the sheet thickness doubles the force.
The shear strength is the material property, the stress at which the metal fails in shear, and it ranges from under 100 N/mm² for soft aluminium to 600 or more for stainless steel, which is why the same tool needs far more force in a hard material than a soft one.
When several features are cut in one stroke and they all shear at the same instant, their forces add, so the total is the sum of each feature’s perimeter-times-thickness-times-shear-strength product; for identical features it is simply one feature’s force times the count. This additive behaviour is why a die that punches many holes at once can demand a very large press, and why staggering the punches or grinding shear angles — so the cuts do not all peak together — is a common way to keep the peak force within a smaller press. The calculator handles the feature count and the shear angle so you can see both effects.
From cut force to press tonnage
The cut force is the theoretical minimum, but the press has to supply more, and the difference is what turns a force into a tonnage rating. First there is the stripping force: once the punch has pierced the sheet, the material grips it, and the stripper has to push the sheet off the punch on the return stroke. That stripping force is a fraction of the cut force — commonly 5 to 20 percent for spring strippers and 25 to 30 percent for urethane — and although it acts on the return, it is part of the load the press system must handle, so it is added to the cut force. The calculator takes the stripping percentage and adds it.
Second there is the safety factor. The theoretical force assumes a sharp tool, ideal clearance, and nominal material; in reality the punch edge wears and needs more force, the clearance between punch and die varies, lubrication changes, and the material’s strength and thickness vary within tolerance. A safety factor of about 1.2 to 1.3 covers this, ensuring the press is not sized right at the theoretical limit where a dull tool or a strong batch of material would stall it. The total press force is the cut force plus the stripping force, multiplied by the safety factor, and it is this number, converted to tonnes or US tons, that you match against a press’s rated capacity.
The convention for stating capacity differs by region and press type. Mechanical and hydraulic presses are rated in tonnes-force or US (short) tons, so the calculator converts the total force from newtons to both kilonewtons and tonnes in metric, or to pounds and US tons in imperial. Always specify a press whose rated capacity exceeds the total force with margin to spare, and remember that a mechanical press’s rated tonnage is only available near the bottom of the stroke — a point that matters for deep operations but not for the thin-sheet cutting this formula covers.
Five worked examples you can follow
Example 1: the default round hole
A 20 mm round hole in 3 mm mild steel with a shear strength of 350 N/mm². The perimeter is π·20 ≈ 62.8 mm, so the cut force is 62.8 × 3 × 350 ≈ 65,970 N. Adding 10 percent stripping and a 1.2 safety factor gives a total of about 87,080 N, roughly 87 kN or 8.9 tonnes — so a 10-tonne press is a sensible choice.
Example 2: estimating from tensile strength
The same hole in a steel for which you only know the tensile strength, 500 N/mm². Enter 500 as the UTS and leave shear blank; the calculator uses about 0.7 × 500 = 350 N/mm², recovering the same result. The shear-strength field is flagged as derived so you know it is an estimate.
Example 3: several holes at once
The same die now punches four of those 20 mm holes in one stroke. The cut force quadruples to about 264,000 N, and the total press force rises to about 348 kN, roughly 35 tonnes. Punching all four together needs a much larger press than one hole — the reason for staggering or shear angles.
Example 4: a shear angle
Return to one hole but grind a shear angle that reduces the peak force by 40 percent. The cut force drops from about 66,000 N to about 40,000 N, and the total press force falls in proportion, letting the job run on a smaller press. The total work is unchanged; only the peak is lower.
Example 5: a press-brake bend
Switch to bending mode: a 100 mm long bend in 3 mm material of 450 N/mm² tensile strength in a 24 mm die. The force is 1.33 × 450 × 100 × 3² ÷ 24 ≈ 22,450 N, about 22 kN or 2.3 tonnes — far less than punching, and it drops further with a wider die.
Three expert tips for reliable results
Use real shear strength
The force scales directly with shear strength, so a data-sheet value for your exact alloy and temper gives the most reliable tonnage. Use the tensile estimate only when you must, and treat it as approximate.
Size on the total, not the cut force
Specify the press against the total force after stripping and safety, not the theoretical cut force. Sizing on the cut force alone leaves no margin for tool wear and material variation.
Use shear angles or staggering for big jobs
When many features punch at once, the peak force can exceed your press. A shear angle or a stepped punch spreads the cuts over the stroke and keeps the peak within capacity.
The mathematics behind the results
The cutting-force formula follows from the definition of shear strength as force per unit sheared area. When a punch shears a closed shape from the sheet, the surface being cut is a thin band running around the perimeter of the shape and through the full thickness of the sheet; its area is the perimeter times the thickness.
Shear strength is the force per unit area at which the material fails in shear, so multiplying it by that area gives the force to shear the whole perimeter at once: F = perimeter × thickness × shear strength.
The feature count multiplies this when several identical shapes cut simultaneously, and the shear-angle factor reduces the peak because a bevel means only part of the perimeter is being cut at any instant.
The stripping and total-force calculations are straightforward proportions. The stripping force is the stripping percentage times the cut force, reflecting that the grip of the sheet on the punch is empirically a fraction of the force that made the cut. The total press force is the sum of the cut force and the stripping force, multiplied by the safety factor, which scales the whole load up to cover wear and variation. The conversions to tonnes and US tons divide the force in newtons by the weight of a tonne (9,806.65 newtons) or the pounds in a US ton (2,000), so the result can be read directly against a press rating in the units it is sold in.
The bending-force formula is an empirical relation for air bending: F = K × tensile strength × width × thickness² ÷ die opening. Here the force rises with the square of thickness, because a thicker sheet resists bending far more strongly, and falls as the die opening widens, because a wider span gives the punch more leverage. The factor K, around 1.33, folds in the geometry of the three-point air bend.
Two assumptions frame all these results: the cutting formula gives the peak shearing force for a clean cut at proper clearance, and the bending formula is the air-bend estimate — bottoming and coining need more, and the constants shift with tooling.
Within those bounds the arithmetic is exact; matching the shear strength, stripping percentage, and safety factor to your real material and tooling is the engineering judgement that makes the tonnage trustworthy.
Where press force calculations are used
Press-force calculation is the foundation of press selection and die design, and it connects to the other forming tools in this silo.
The blank whose force this tool computes is the same blank whose flat size is set by the bend allowance calculator — one tool sizes the developed blank, this one sizes the press that cuts or bends it.
In tool-and-die work, the punching force determines the press tonnage, the die-set size, and the stripper design, and the same force, distributed over the punch face, sets the compressive stress the tooling steel must withstand. Underestimating the force stalls the press or breaks the tool; overestimating it buys more press than the job needs.
In production and estimating, the tonnage feeds machine selection and scheduling, since a job can only run on a press with enough capacity, and the force influences the energy per stroke and therefore the strokes-per-minute a press can sustain.
It bears on tool life, because higher forces wear punch and die edges faster, and on part quality, since the clearance and force together set the quality of the sheared edge. This calculation also links to the machining side of the silo through the shared discipline of relating a material property — shear strength here, cutting speed there — to the force or power a process demands.
Return to the Manufacturing Processes hub for the companion tools across machining, forming, and molding.
Beyond the individual operation, press force informs safety, capital planning, and process choice. A press must never be loaded beyond its rating, so the force calculation is a safety calculation as much as a productivity one; it guides the purchase or specification of new presses, a major capital decision; and it shapes the choice between processes, such as whether to punch a feature, laser-cut it, or nibble it, each with a different force and cost profile. Accurate force estimates are what let a fabricator match the tool, the press, and the part with confidence.
Shear strength reference by material
When you do not have a measured value, these typical shear strengths give a defensible starting point. They vary with alloy, temper, and condition, so treat them as ranges and use a data-sheet value for precise work. Where only tensile strength is known, shear strength is roughly 0.6 to 0.8 of it, and this calculator uses about 0.7 by default.
| Material | Shear strength (N/mm²) | ≈ (psi) |
|---|---|---|
| Aluminium (soft to alloyed) | 70 – 200 | 10,000 – 29,000 |
| Copper (annealed) | 150 – 250 | 22,000 – 36,000 |
| Brass | 250 – 350 | 36,000 – 51,000 |
| Mild / low-carbon steel | 250 – 350 | 36,000 – 51,000 |
| Stainless steel 304 | 500 – 600 | 73,000 – 87,000 |
| Spring / high-carbon steel | 550 – 700 | 80,000 – 102,000 |
Read these against the thickness and perimeter of your cut. A hard material in a thick sheet with a long cut line stacks all three force drivers and can demand surprising tonnage; a soft, thin material with a short perimeter needs little. The table seeds the calculator; a data-sheet shear strength, or a tensile value converted at your own ratio, gives the precise figure for a critical job.
Cutting clearance and edge quality
The clearance between the punch and the die — the small gap on each side, usually expressed as a percentage of the sheet thickness — is not part of the force formula, but it shapes how the cut behaves and is worth understanding alongside the force.
When clearance is correct, typically around 5 to 10 percent of thickness per side for common steels and a little less for soft metals, the cracks that start at the punch and die edges meet cleanly, giving a good sheared edge with a modest burnished band and a manageable burr, at close to the theoretical force.
When clearance is too small, the cracks miss each other, a secondary shearing occurs, and the force rises and the tool wears faster; when it is too large, the material draws in and the edge tears with a large burr.
Clearance therefore interacts with the force in two ways. First, wrong clearance raises the actual force above the theoretical value, which is one of the variations the safety factor is meant to cover. Second, the goal of a clean edge often sets the clearance, and that in turn influences tool life and the force stability over a production run. The calculator computes the force at proper clearance; if you know your clearance is tight or your tooling is worn, lean toward the higher end of the safety factor so the press has margin for the extra force those conditions demand.
A useful way to use the formula in reverse is to find the largest hole or thickest sheet a given press can handle. Rearranging F = perimeter × thickness × shear strength, the maximum thickness a press of a known tonnage can punch for a given hole is the rated force divided by the perimeter times the shear strength, after allowing for stripping and safety.
Working the calculation backwards like this turns the tool into a capability check: enter a trial thickness or perimeter, read the total force, and compare it to the press you have, adjusting until the total sits comfortably below the rating.
It is the same arithmetic viewed from the other end, and it is how a shop decides whether an existing press can take on a new part before committing to tooling.
Blanking versus punching: the same force, different scrap
Punching and blanking use the identical force formula but differ in which piece is the product, and the distinction matters for tooling and for where any shear angle goes. In punching, the slug that is pushed out is scrap and the sheet with the hole is the product, so the hole must be to size, which means the die sets the size and the punch is smaller by the clearance. In blanking, the piece pushed out is the product and the surrounding sheet is scrap, so the blank must be to size, which means the punch sets the size and the die is larger by the clearance. The force is the same — perimeter times thickness times shear strength — because the same perimeter is sheared either way.
The practical consequence is where you can afford to distort the edge. A shear angle grinds a bevel that slightly dishes the piece it faces, so it is put on the scrap side: on the punch face for punching, where the slug is scrap, and on the die face for blanking, where the skeleton is scrap, keeping the product flat. This is why the shear-angle reduction in the calculator is a tooling choice tied to whether you are punching or blanking, not a free reduction you can always apply. Knowing which operation you are running tells you whether the reduced peak force is actually available for your product quality.
Force, energy and the press stroke
The tonnage this calculator reports is the peak force, and for selecting a press that peak is usually the binding number, but energy per stroke is a second consideration on mechanical presses.
A mechanical press stores energy in a flywheel and delivers it over the working part of the stroke; its rated tonnage is available only near the bottom of the stroke, and the energy the flywheel holds limits how much work each stroke can do.
For thin-sheet cutting the punch travels only a fraction of the thickness before the material fractures, so the work per stroke is small and the peak force is what matters. For thicker material or deep forming, the work can be large enough that energy, not just force, sets whether the press can make the part at the desired speed.
This is why the peak-force calculation here is the right tool for punching, blanking, and shearing, and why bending and deep operations may need an energy check in addition. It also explains why running many strokes per minute can be limited by how fast the flywheel recovers its energy between strokes, not by the force. For the sheet-cutting operations this calculator targets, size the press on the total force with margin and the energy will follow; for heavy forming, treat the force as necessary but confirm the press has the stroke energy as well.
Common mistakes to avoid
A few errors recur in press-force calculations. Watch for them.
- Using area instead of perimeter. Cutting force depends on the length of the cut edge, not the area enclosed. A long slot can need as much force as a big hole; always use the perimeter.
- Confusing shear strength with tensile strength. Shear strength is roughly 0.6 to 0.8 of tensile. Entering the tensile value as if it were shear overstates the force by a third or more.
- Sizing on the cut force alone. The press must supply the cut force plus stripping, with a safety margin. A press rated exactly at the cut force will stall as the tool wears.
- Ignoring simultaneous features. Several holes punched at once add their forces. Sizing for one hole when the die cuts six underestimates the tonnage sixfold.
- Forgetting the die opening in bending. Bending force depends strongly on the die V-width and the square of thickness. Using the wrong die opening can be off by a large factor.
- Treating a shear angle as free. A shear angle lowers the peak force but can distort the part and complicate the tool; use it deliberately, not as a default assumption in the number.
Input format and quick reference
Choose an operation and units, then enter the thickness and either the shear strength or the tensile strength; for cutting add the perimeter, feature count, shear-angle reduction, and stripping percentage; for bending add the width and die opening. The reference below explains each output.
| Output | What it means |
|---|---|
| Total press force | The capacity to specify; (cut + stripping) × safety, in kN and tonnes (or lbf and US tons) |
| Cut / punch force | The theoretical shearing force; perimeter × thickness × shear strength |
| Stripping force | Force to pull the punch out; the stripping percentage of the cut force |
| Shear strength used | The value applied, flagged if derived from tensile strength |
Frequently asked questions
How do I calculate punching force?
Punching force is the force needed to shear a shape out of sheet metal, and it is the product of three things: the perimeter of the cut, the material thickness, and the material’s shear strength. The formula is F = perimeter × thickness × shear strength. The perimeter is the total length of the cut edge — for a round hole it is π times the diameter, and for a profile it is the length of the whole outline.
Thickness is the sheet thickness the punch has to cut through, and shear strength is the stress at which the material fails in shear, taken from a data sheet. For a 20 mm round hole in 3 mm mild steel with a shear strength of 350 N/mm², the force is π·20 × 3 × 350 ≈ 66,000 N, about 6.7 tonnes.
This calculator does that calculation and adds the stripping force and a safety factor to give the total press force.
What is the difference between punching force and press tonnage?
Punching force, or cut force, is the theoretical force to shear the material — perimeter times thickness times shear strength.
Press tonnage is the capacity you actually need to specify for the press, and it is larger, because it includes the stripping force needed to pull the punch back out of the sheet and a safety margin for tool wear, clearance variation, and material variation.
A common approach is to add a stripping allowance of roughly 5 to 20 percent of the cut force and then a safety factor of about 1.2 to 1.3. The calculator reports both: the raw cut force and the total press force after stripping and safety, and it converts the total to kilonewtons and tonnes (or pounds and US tons) so you can match it to a press rating directly.
What shear strength should I use?
Use the shear strength for your specific material from a data sheet whenever you can, because it varies widely: as rough guidance, low-carbon mild steel is around 250 to 350 N/mm², stainless steel 304 around 500 to 600, aluminium alloys around 70 to 200 depending on temper, copper around 200 to 250, and brass around 250 to 350.
If you only have the tensile strength (UTS), you can estimate shear strength as roughly 0.6 to 0.8 times the tensile strength; this calculator will do that estimate for you if you enter the UTS and leave the shear strength blank.
The estimate is good enough for sizing a press, but for a precise force — for example to protect a delicate tool — use the measured shear strength for the exact alloy and temper.
What is stripping force?
Stripping force is the force required to pull the punch back out of the sheet after it has cut through. As the punch pierces the material, the sheet grips the punch, and the stripper — a spring, urethane pad, or fixed plate — must overcome that grip to separate them on the return stroke.
It is usually a fraction of the punching force, commonly around 5 to 20 percent for spring strippers, and higher, 25 to 30 percent, for urethane strippers depending on their hardness and compression. Stripping force matters because the press and the stripper system must supply it, and because it adds to the total load the press sees in a cycle.
The calculator lets you enter the stripping percentage and includes it in the total press force.
How does a shear angle reduce the force?
Grinding a shear angle, or bevel, onto the face of the punch or die spreads the cut over the punch stroke instead of shearing the whole perimeter at once. Without a shear angle, the entire cut happens at one instant and the peak force is the full perimeter times thickness times shear strength.
With a shear angle, only part of the edge is cutting at any moment, so the peak force drops — often by a third to a half, depending on the angle — even though the total work is the same. This lets a given job run on a smaller press or reduces shock and noise. The trade-off is that shear can distort the part slightly, so it is used more on scrap-side cuts.
The calculator has a shear-reduction input so you can estimate the reduced peak force.
How do I calculate force for several holes at once?
If a die punches several holes or features in the same stroke, and they all cut at the same instant, the forces add: the total cut force is the sum of the individual perimeter × thickness × shear-strength products.
If every feature is identical, that is simply the single-feature force multiplied by the number of features, which is what the calculator’s feature-count input does.
This matters because punching many holes at once can demand far more tonnage than a single hole, and it is a common reason a job needs a larger press or a staggered (shear-angled or stepped) tool that spreads the cuts across the stroke so they do not all peak together. If your features differ, calculate each and add them, or use the largest-perimeter case to size the press.
How do I calculate bending force on a press brake?
Bending force is a different calculation from cutting force. For air bending, a common estimate is F = K × tensile strength × width × thickness² ÷ die opening, where K is a factor around 1.33, the width is the length of the bend, the thickness is the material thickness, and the die opening is the V-width of the die. Force rises with the square of thickness and falls as the die opening widens, which is why a wider die dramatically lowers the tonnage a bend needs. This calculator has a bending mode that applies this formula, so you can size a press brake for a bend as well as a press for a cut. Bottoming and coining need more force than air bending for the same part.
Does this calculator store the numbers I enter?
No. The calculator runs entirely in your browser. The dimensions, material properties, and any other values you enter are never sent to our servers, stored, or shared. You can download a PDF or CSV of your results locally, and nothing leaves your device. See our Privacy Policy for details.
Is the press force calculator free?
Yes. The press and stamping force calculator is completely free, with no account, sign-up, or usage limit. It computes punching, blanking, and shearing force from perimeter, thickness, and shear strength; adds stripping force and a safety factor for the total press tonnage; estimates shear strength from tensile strength; models a shear angle and multiple features; includes a bending-force mode; works in metric or imperial units; plots force against thickness; and exports to PDF and CSV, all at no cost.
Related manufacturing process calculators
More tools in this silo. Return to the Manufacturing Processes hub for the full set.
Sources, disclaimer and editorial transparency
This calculator uses the standard sheet-metal relations: cutting force F = perimeter × thickness × shear strength; stripping force as a percentage of the cut force; total press force = (cut + stripping) × safety factor; the air-bending estimate F = K · UTS · width · T² / V with K ≈ 1.33; and shear strength ≈ 0.6–0.8 × tensile strength, consistent with standard press-tool and metalforming references.
Typical shear-strength values are published ranges for general guidance. This calculator and guide are created and reviewed by the OpsCalculators team; see our Editorial Policy for how each tool is researched, built, and tested.
Results are accurate estimates for press selection, tool design, and education, not a substitute for verified material data or a press manufacturer’s ratings. Actual forces vary with clearance, tool wear, lubrication, and material condition. See our full Disclaimer. OpsCalculators.com is operated by MAFHH INTERNATIONAL LTD. Your data is processed in your browser and never stored; see our Privacy Policy.