Application and capacity
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Press brake planning
Press Brake Tonnage Planning Guide
Calculate required press brake tonnage, then verify the material, bend length, V-die opening, bending method and tooling limits.
This tool provides a planning estimate for common air-bending scenarios. It is not a setup instruction and does not replace the press brake or tooling manufacturer's tonnage chart.
Inputs that affect required tonnage
- Material type, thickness, tensile strength, and bend length
- Die opening, punch radius, bend angle, and bending method
- Tooling condition, load position, and machine deflection
Use the result safely
Verify the calculation against the specific machine rating, tooling capacity, and supplier charts. Never exceed the rated capacity of the press brake, tooling, adapters, or workholding system. Off-center loads and special bending methods can change allowable capacity. Only trained personnel should set up and operate the machine.
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Press Brake Tonnage Calculator
Air bend, bottoming and coining force, plus the two limits most calculators leave out: tons per inch against your tooling, and the 60 % span rule against your machine bed.
The bend
Gauge numbers are Manufacturers’ Standard Gauge for steel sheet. Aluminum sheet uses a different gauge series — for aluminum, type the decimal thickness instead.
0.250 in (6.35 mm)
24 in (610 mm)
Your machine — optional, unlocks the limits check
Estimated force required
Tons per foot
—tons/ft
Total for this bend
—tons
With 20 % safety margin
—tons
Tooling and geometry
- Recommended V-die (8 × t)—
- V-die used in this calculation—
- Estimated inside radius (0.16–0.17 × V)—
- Minimum flange (0.67 × V)—
- Load concentration—
Limits check
The math, in full
1. Base air-bend force, per foot of bend:
T = (650 × t²) ÷ V
where t is material thickness in inches and V is the V-die opening in inches. The constant 650 is the force needed to air bend one foot of mild steel at roughly 60,000 PSI tensile strength. Every figure this calculator produces starts here.
2. Material factor — multiply the base figure by:
- Mild steel — × 1.0 (the constant is already calibrated to mild steel)
- Stainless 304 — × 1.5
- Soft aluminum (5052-H32) — × 0.5
- Aluminum 6061-T6 — calculated at the same × 0.5 soft-aluminum factor. Harder tempers run higher. We do not publish a 6061-T6 factor because we will not invent one — verify for your temper with your material certificate and your tooling supplier.
3. Method factor — multiply again by:
- Air bending — × 1
- Bottoming — × 4 to × 5 (shown as a range, because it depends on how far into the die you set the ram)
- Coining — × 10
4. Total force for the bend:
Total tons = tons per foot × (bend length in inches ÷ 12)
5. Safety margin: the 20 % figure is total × 1.2. Size the machine against the margin figure, not the raw figure. Material thickness runs over nominal, tensile strength varies heat to heat, and a die that is 10 % narrower than planned raises force sharply.
6. Geometry: inside radius r ≈ 0.16 to 0.17 × V for air bending; minimum usable flange ≈ V × 0.67. Below that flange length the part slips off the die shoulder.
Units: all tonnage on this page is US short tons (2,000 lb). Multiply by 0.907 for metric tonnes.
Why the limits check matters more than the tonnage number
A tonnage figure on its own tells you whether the machine can make the bend. It does not tell you whether the bend will damage the tooling or the machine. Two separate limits get shops into trouble, and neither is usually published:
Tons per inch — the tooling limit. Divide total tonnage by bend length in inches. Standard punch and die profiles are typically rated somewhere in the 4 to 12 tons per inch band, depending on profile, material and hardness. Exceed the rating and you brinell the punch tip or crush the die shoulder — usually before you notice anything wrong with the part. Tooling hardness and its effect on load rating is discussed by Jeelix, which also notes the common practice of derating tooling to 70–80 % of its published maximum for continuous production.
The 60 % span rule — the machine limit. A press brake’s rated tonnage assumes the load is spread across the bed. Concentrate the full rating into a short bend near the center and you can permanently bow the bed and the ram. ADH Machine Tool publishes the working rule:
safe tons per foot = rated tonnage ÷ (0.60 × span between housings, in feet)
Enter your machine’s rated tonnage and span above and the limits panel will run both checks against your bend.
Press brake tonnage chart — air bending at an 8 × t V-die
| Thickness | V-die (8 × t) | Mild steel (tons/ft) | Stainless 304 (tons/ft) | Aluminum 5052 (tons/ft) |
|---|---|---|---|---|
| 16 ga — 0.060 in (1.52 mm) | 0.48 in (12.2 mm) | 4.9 | 7.3 | 2.4 |
| 14 ga — 0.075 in (1.91 mm) | 0.60 in (15.2 mm) | 6.1 | 9.1 | 3.0 |
| 11 ga — 0.120 in (3.05 mm) | 0.96 in (24.4 mm) | 9.8 | 14.6 | 4.9 |
| 3/16 in — 0.1875 in (4.76 mm) | 1.50 in (38.1 mm) | 15.2 | 22.9 | 7.6 |
| 1/4 in — 0.250 in (6.35 mm) | 2.00 in (50.8 mm) | 20.3 | 30.5 | 10.2 |
| 3/8 in — 0.375 in (9.53 mm) | 3.00 in (76.2 mm) | 30.5 | 45.7 | 15.2 |
| 1/2 in — 0.500 in (12.70 mm) | 4.00 in (101.6 mm) | 40.6 | 60.9 | 20.3 |
All figures are tons per foot of bend. For a 4-foot bend, multiply by 4. For bottoming multiply by 4–5; for coining multiply by 10. Add 20 % before you size a machine against these numbers.
At an 8 × t die the tonnage-per-foot figure scales linearly with thickness, which is why the mild-steel column is simply 81.25 × thickness. That relationship only holds while the die opening tracks thickness — if you keep a 2 in die on the machine and run 16 ga through it, the force drops far below the table.
Sources and method attribution
- Tonnage formula and the 650 constant — ADH Machine Tool, What is press brake tonnage
- 60 % span rule for safe tons per foot on short bends — ADH Machine Tool, Press brake bending capacity
- Tonnage chart methodology cross-check — RMFG, Press brake tonnage chart and calculator
- V-opening selection, inside radius and minimum flange relationships — WILA, V-opening
- Material and method multipliers cross-check — MachineMFG, Press brake tonnage calculator
- Tooling hardness, load rating and the 70–80 % derate practice — Jeelix, Press brake tooling hardness
Results are estimates for planning and machine sizing. Actual force varies with heat lot, grain direction, die condition and ram setting — final tooling and machine specification requires a quote review with your part drawings.