1. Press Brake Tonnage Calculator

Enter the material tensile strength, sheet thickness, bend length, and die V-opening below. The calculator estimates the force required for conventional 90-degree air bending.

2. What Is Press Brake Tonnage?

Press brake tonnage is the amount of force the machine applies during bending. Machine capacity is commonly expressed in metric tons, US tons, or kilonewtons.

Tonnage is not determined by thickness alone. Two jobs using the same thickness can require very different forces if the material, bend length, or V-opening changes.

A press brake rated at 100 tons does not mean every tool can safely carry 100 tons in every setup. Tool length, tool rating, clamping, load distribution, and machine geometry must also be considered.

3. Press Brake Air-Bending Force Formula

A commonly used engineering relationship for estimating conventional 90-degree air-bending force is:

When tensile strength is entered in N/mm², sheet thickness and bend length in millimeters, and V-opening in millimeters, the result is approximately in newtons. Divide by 1,000 for kilonewtons, then divide by 9.80665 to obtain metric ton-force.

This is an estimating formula. Actual force can differ because of die shoulder geometry, friction, bend angle, grain direction, material variation, tooling condition, and machine/tooling design.

4. Understanding the Tonnage Formula

5. Material Tensile Strength and Tonnage

Material strength has a direct effect on bending force. A stronger material requires more force to produce the same bend.

Typical values used for preliminary estimates may include approximately 450 MPa for common mild steel, around 600 MPa for many stainless-steel applications, and around 300 MPa for some aluminum alloys.

These are only example values. Actual tensile strength can differ substantially by grade, temper, heat treatment, and material standard. Use the real material specification whenever possible.

6. How Die V-Opening Changes Required Tonnage

The V-opening is one of the easiest ways to change required bending force.

A larger V-opening reduces force because the sheet spans a greater distance between the die shoulders.

A smaller V-opening increases force and typically creates a tighter natural inside radius.

For common mild-steel air bending, a V-opening around six to eight times material thickness is often used as an initial selection range for thinner sheet, but the correct choice depends on radius, flange size, marking, material strength, and tooling limits.

Read our Press Brake Tooling Guide for detailed V-opening selection.

7. Why Sheet Thickness Has Such a Large Effect on Tonnage

Thickness appears squared in the common air-bending equation. This means increasing thickness has a much larger effect than increasing bend length by the same percentage.

For example, if all other variables remain unchanged, doubling sheet thickness theoretically increases the estimated bending force by about four times.

In practice, thicker sheet is normally paired with a larger V-opening, which offsets part of that increase.

8. How Bend Length Affects Tonnage

Bending force increases approximately in direct proportion to bend length.

If a one-meter bend requires 20 metric tons under a particular setup, a two-meter bend under the same conditions would require approximately 40 metric tons.

This is why tonnage-per-meter values are useful when comparing tooling and machine capacity.

9. Air Bending vs Bottom Bending vs Coining Tonnage

Air bending normally requires the least force because the material is supported at the die shoulders and does not fully conform to the die.

Bottom bending requires substantially more force because the sheet is driven deeper into the tool geometry.

Coining requires very high force because the material is plastically compressed into the punch and die geometry.

Do not use a simple air-bending calculator to size a coining operation.

10. Press Brake Tonnage Calculation Examples

Example 1: 2 mm Mild Steel, 1 Meter Bend

Assume tensile strength of 450 MPa, thickness 2 mm, bend length 1,000 mm, and V-opening 16 mm.

The estimated force is approximately 160 kN, or about 16 metric tons.

Example 2: Same Material but 2 Meter Bend

Keeping the same thickness and V-opening but increasing bend length to 2,000 mm approximately doubles the required force to about 320 kN, or roughly 33 metric tons.

Example 3: Smaller V-Opening

If the V-opening is reduced while all other inputs remain unchanged, required force rises because V is in the denominator of the formula.

11. Quick Mild-Steel Air-Bending Tonnage Chart

The table below gives approximate values using 450 MPa tensile strength and a V-opening near eight times material thickness. It is intended only for preliminary selection.

Approximate engineering values only. Real tooling charts should be used for production decisions.

12. Understanding Tonnage per Meter

Tonnage per meter makes it easier to compare jobs with different bend lengths.

If a setup requires 30 tons per meter and the bend is 2.5 meters long, the estimated total force is approximately 75 tons.

Tooling is also frequently rated by allowable force per meter or per unit length, so this value is important for both machine and tool safety.

13. Tooling Load Limits

The press brake may have more capacity than the installed tooling.

Every punch, die, adapter, and clamp has an allowable load.

Gooseneck punches and thin acute punches may have lower load capacity than heavy straight tools because their cross-section is smaller.

Never assume that a 200-ton press brake can safely apply 200 tons through any tool.

Check the tooling manufacturer’s load chart before high-tonnage bending.

14. Press Brake Machine Capacity

A machine’s nominal tonnage normally describes the maximum rated total force under specified loading conditions.

The full rating may depend on how the load is distributed along the bed.

Machine frame, cylinders, ram, bed, hydraulic system, and crowning system are designed around specific load limits.

Do not intentionally exceed the machine’s rated tonnage even if the tool appears strong enough.

15. Off-Center Loading

A short bend placed far from the center of the press brake can create uneven loading on the machine.

Machine builders may specify limits for off-center loading or require particular setup practices.

Where possible, distribute loads appropriately and follow the machine manufacturer’s instructions.

Do not assume that a low total tonnage automatically makes an extreme off-center setup acceptable.

16. Short Bends and Concentrated Tool Load

A short bend may use relatively low total tonnage while still creating high force per meter.

This is important for segmented tools and narrow punches.

For example, applying 20 tons over a 200 mm segment corresponds to 100 tons per meter of local loading.

Always compare concentrated load with the rating of the actual tool segment.

17. Press Brake Tonnage for Stainless Steel

Stainless steel generally has higher tensile strength than common mild steel, so it usually requires more bending force for the same thickness, bend length, and V-opening.

It also tends to exhibit more springback.

Use the actual tensile-strength specification for the stainless grade whenever available rather than applying one universal correction factor.

18. Press Brake Tonnage for Aluminum

Many aluminum alloys require less bending force than mild steel, but the difference depends strongly on alloy and temper.

Some high-strength aluminum grades can behave very differently from soft aluminum.

Aluminum may also require special attention to inside radius and surface marking.

19. High-Strength Steel Tonnage

High-strength steel can require significantly more bending force than conventional mild steel.

Its springback and minimum-radius requirements can also be greater.

Tooling that is adequate for mild steel may become overloaded when high-strength material is introduced.

Use the real tensile strength and follow the material supplier’s bending recommendations.

20. Inside Radius, Die Opening and Tonnage

In air bending, die V-opening strongly influences the natural inside bend radius.

A larger opening generally creates a larger radius and reduces required force.

A smaller opening creates a tighter natural radius but increases tonnage.

Tool selection should therefore balance radius requirement, flange size, force, marking, and tool capacity.

21. Minimum Flange Length and V-Opening

The workpiece flange must remain supported across the die shoulders during bending.

A very large V-opening may reduce tonnage but make a short flange impossible to support properly.

This is why choosing the largest possible die opening is not always the correct solution.

Read the Press Brake Tooling Guide for more detail on minimum flange and V-opening selection.

22. Step-by-Step Press Brake Tonnage Selection

23. Common Press Brake Tonnage Mistakes

24. Tonnage in CNC Press Brake Programming

Modern CNC controllers use material, thickness, tooling, and product data to help calculate bending parameters.

Advanced Delem controls can integrate product programming, tooling libraries, bend sequence, crowning, and machine simulation.

However, the operator and process engineer remain responsible for verifying actual machine and tooling capacity.

Read our Press Brake Programming Guide and Delem CNC Controller Knowledge Center for more information.

25. Frequently Asked Questions About Press Brake Tonnage

What is press brake tonnage?

It is the force required or available to bend sheet metal on a press brake.

How do I calculate press brake tonnage?

For conventional air bending, estimate force from tensile strength, sheet thickness squared, bend length, and die V-opening, then verify the result with the manufacturer’s bending chart.

Does thicker sheet require more tonnage?

Yes. Force increases strongly with thickness.

Does a longer bend require more force?

Yes. Required force increases approximately in direct proportion to bend length.

Does a larger V-opening reduce tonnage?

Yes, generally. However, it also changes inside radius and minimum flange requirements.

Why does stainless steel need more tonnage?

Many stainless grades have higher tensile strength than common mild steel.

Does aluminum require less tonnage?

Many aluminum alloys do, but the correct value depends on alloy and temper.

Can I use the machine’s maximum tonnage on any tool?

No. Punches, dies, adapters, and clamps have their own load limits.

What does tons per meter mean?

It is bending force normalized to one meter of bend length.

Why are short bends dangerous for tooling?

A short bend can concentrate significant force into a small tool segment even when total force is modest.

Does bottom bending need more force than air bending?

Yes, generally.

Does coining require more force?

Yes. Coining can require dramatically more force than air bending.

Can I use this calculator for coining?

No. It is intended for preliminary conventional air-bending estimates.

What V-opening should I use?

For common mild-steel air bending, six to eight times material thickness is a common starting range for thinner sheet, but actual selection depends on the application.

Can a smaller V-opening make a tighter radius?

Yes, generally, but it also increases required force.

Can a larger V-opening damage accuracy?

It may increase the natural radius and can make short flanges difficult to bend.

What tensile strength should I use?

Use the actual material specification whenever possible.

Is nominal sheet thickness accurate enough?

For general estimates it may be, but precision work benefits from measuring actual thickness.

What happens if the press brake is undersized?

The machine may be unable to complete the bend or may operate outside its intended range.

What happens if tooling is overloaded?

Tooling may deform, crack, or fail and can create a serious safety risk.

Should I add extra tonnage as a safety margin?

Machine selection should include reasonable capacity margin, but production force should never intentionally exceed tool or machine ratings.

Does grain direction affect tonnage?

Material behavior can vary with rolling direction, although tensile strength, thickness, length, and V-opening remain the main calculation inputs.

Does bend angle affect force?

Yes. The simple calculator is intended for conventional approximately 90-degree air bending; other geometries can change force requirements.

Can Delem calculate bending force?

Delem-equipped press brakes can use material and tooling data as part of the programmed bending process, depending on controller and machine integration.

Where can I learn about punch and die selection?

Read the YRS Industrial Press Brake Tooling Guide linked below.

26. Related YRS Industrial Guides

• Press Brake Tooling Guide: How to Choose the Right Punch and Die
• Press Brake Programming Guide
• Delem CNC Controller Knowledge Center
• Delem Profile-T Complete Guide
• Delem Profile-S Complete Guide
• Delem Error Codes & Troubleshooting Guide

27. Need Help Choosing the Correct Press Brake Tonnage?

YRS Industrial supplies CNC press brakes, tooling, and sheet metal fabrication equipment. If you are unsure what machine tonnage you need, send us your bending requirements and part drawings.

For a machine recommendation, send your material type, tensile strength if known, maximum thickness, maximum bending length, typical part drawings, required inside radius, and destination country or port.

Technical Reference Note

For common steel air bending, tooling specialists such as WILA describe V-opening selection as a major determinant of natural product radius, bending force, minimum leg length, and marking. A V-opening around six to eight times sheet thickness is a commonly used starting range for steel around 450 N/mm² in thinner gauges. Always follow the specific tooling and machine manufacturer’s recommendations for production.