Press brake

Press Brake Tonnage Calculator

Estimate only: actual tonnage and radius depend on material tensile, grain direction, springback, and tooling condition. Verify machine capacity and tooling load limits before operation.

Air-bending screening estimate ONLY — not a machine setting or a verified safe operating load. Tonnage is expressed in US short tons (2,000 lbf), not metric tonnes-force; millimeter dimensions are converted to inches before the imperial formula. Bottoming, coining, acute bends, small V openings, friction and die wear can increase actual force. Verify the manufacturer's machine load-distribution/concentrated-load limits and the punch and die load rating per unit length before operating.

Estimate air-bending tons per foot and total machine tonnage from thickness, V-die opening, bend length, and a material multiplier. Use the result to plan tooling and machine selection — never as a final load number.

mild steel16 ga0.0598 in1.519 mm

Interactive calculator

Press Brake Tonnage Calculator

MaterialGaugeThickness

V-die opening

Bend length

Tons per foot5.73 tons/ft

Total tonnage22.92 tons

Material multiplier1x

Estimate only: actual tonnage and radius depend on material tensile, grain direction, springback, and tooling condition. Verify machine capacity and tooling load limits before operation.

Assumptions

Verify before production

Calculator values are estimates. Confirm bend deductions, springback, tooling, grain direction, coating condition, and safe tonnage with the material and tooling supplier before production.

Air bending and common gauge tables are assumed unless edited.
Actual results vary by tooling, grain direction, coating, temper, and springback.
Machine capacity and tooling load ratings must be checked independently.
Result is a screening estimate for shop planning. Verify against material certificate, tooling chart, machine rating, and a coupon test before production.
AIR BENDING ONLY. Do not apply this estimate to bottoming, coining or acute-angle setups; these can require substantially greater force. Follow the machine and tooling manufacturer's chart.
Reported tons are US short tons (2,000 lbf), not metric tonnes-force. Inputs in mm must first be converted to inches; the calculator does this internally.
The 575 constant is a shop screening approximation, not a normative press setting. Smaller V openings raise force sharply; die wear, friction, tensile/temper variation, grain direction and tooling geometry can change the load.
Check supplier-rated tons per foot and press-brake concentrated-load/distribution limits, especially for short bends. Never rely on nominal press capacity alone.
Press brake machine tonnage rating and load distribution.
Tooling load rating from the punch and die manufacturer.
Material certificate (temper, grain direction, coating condition).
Shop's own coupon-bend records for this material and gauge.
Manufacturer documentation for any non-standard tooling, hemming, or coining.

Default material and formula constants are documented at /reference/data-sources/.

Static reference

Common V-die and tonnage combinations

Swipe table horizontally for more columns.

Gauge	Thickness	Recommended V	Inside radius estimate	48 in bend tonnage
20 ga	0.0359 in / 0.912 mm	0.2154 in	0.0345 in	13.76 tons
16 ga	0.0598 in / 1.519 mm	0.3588 in	0.0574 in	22.92 tons
12 ga	0.1046 in / 2.657 mm	0.6276 in	0.1004 in	40.1 tons
10 ga	0.1345 in / 3.416 mm	1.076 in	0.1722 in	38.67 tons

Formula used

What this calculator computes

T_ft = (575 × M × t²) / V

T_ft: Tons per foot of bend length (tons/ft)
575: Empirical air-bend constant for mild steel in imperial units (—)
M: Material multiplier vs mild steel (1.0 baseline) (ratio)
t: Material thickness (in)
V: V-die opening (top width of the female die) (in)

The 575 constant is a widely circulated shop rule of thumb for air bending mild steel with t and V in inches and the result in tons per foot. It is not from a single normative standard — manufacturer charts vary.
Metric inputs are converted to inches before the formula runs; the constant itself remains imperial-rooted.
Material multipliers shipped with this calculator are starting estimates per family/temper — see /reference/data-sources/.

T_total = T_ft × (L / 12)

T_total: Total tonnage required for the bend length (tons)
T_ft: Tons per foot of bend length (from the formula above) (tons/ft)
L: Bend length (in)

Worked example

One numeric walk-through

Inputs

Thickness t: 0.125 in (1/8")
V-die opening V: 1.000 in
Bend length L: 48 in (4 ft)
Material multiplier M: 1.0 (mild steel baseline)

Steps

t² = 0.125 × 0.125 = 0.015625.
T_ft = (575 × 1.0 × 0.015625) / 1.0 = 8.984 tons/ft.
T_total = 8.984 × (48 / 12) = 35.94 tons.

Result

About 9 tons/ft and 35.9 tons total for this 4-ft bend. Verify against the press brake's rated tonnage AND against the punch and die tooling load ratings before forming.

Common mistakes

Things to check before trusting the number

Treating the result as the maximum machine load — the press's centerline rating, off-center load distribution, concentrated-load allowance for short bends, and tooling rating may all be lower.
Using mild-steel multipliers for stainless or high-strength alloys.
Using the air-bend formula for bottoming or coining — those typically require 2–10× more tonnage.
Forgetting that the 575 constant is imperial; the calculator handles unit conversion, but cross-checking with metric supplier charts requires the correct constant for those charts.

FAQ

Specific checks for this calculator

Is press brake tonnage calculated per foot?

Most air-bending charts start with tons per foot, then multiply by bend length in feet to estimate total required tonnage. This calculator does both steps.

Why is stainless tonnage higher than mild steel?

Stainless typically has higher tensile strength and work-hardening behavior, so the calculator applies a multiplier (~1.5× for 304, ~1.6× for 316) versus the mild-steel baseline.

How do I estimate press brake tonnage in millimeters?

Select mm for input dimensions. The calculator converts thickness, V-die opening, and bend length to inches before applying its imperial-rooted screening formula. Check the unit shown beside the output and compare only with the machine/tooling manufacturer's matching load units.

Why does a wider V-die opening reduce estimated bending force?

With material, thickness and bend length fixed, the screening formula divides by V-die opening. A larger opening lowers its estimated load, but also changes the produced inside radius and minimum flange. Recheck the V-die calculator and actual tooling charts before choosing an opening.

Does a tonnage estimate prove that my press brake is safe?

No. Nominal machine capacity alone does not establish safe local load or tooling capacity. Check the manufacturer's load-distribution chart, punch and die ratings, material specification, setup, and trial-bend procedure before production.

Press Brake Tonnage Calculator

Press Brake Tonnage Calculator

Common V-die and tonnage combinations

What this calculator computes

One numeric walk-through

Inputs

Steps

Result

Things to check before trusting the number

Move between connected shop calculations

Specific checks for this calculator

Is press brake tonnage calculated per foot?

Why is stainless tonnage higher than mild steel?

How do I estimate press brake tonnage in millimeters?

Why does a wider V-die opening reduce estimated bending force?

Does a tonnage estimate prove that my press brake is safe?