# Press Brake Tonnage Calculator

> Source: https://netray.co/tools/press-brake-tonnage-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Estimate the force needed to air bend, bottom or coin a part, then check it against your press capacity and the minimum flange.

## Category

manufacturing

## Industry

Sheet Metal Fabrication

## Audience

- Press brake operator
- Fabrication engineer
- Maintenance planner
- Estimator

## Tool

**Kind:** calculator

**Inputs:**

#### Material tensile strength

**Key:** uts

**Type:** select

**Default:** 400

**Options:**

##### Aluminum 5052-H32 (about 230 MPa)

**Value:** 230

##### Mild steel (about 400 MPa)

**Value:** 400

##### Stainless 304 (about 600 MPa)

**Value:** 600

##### High-strength steel (about 800 MPa)

**Value:** 800

**Help:** Use the mill certificate value for the actual lot if you have it.

#### Thickness

**Key:** t

**Type:** number

**Default:** 2

**Min:** 0.3

**Max:** 25

**Step:** 0.1

**Unit:** mm

#### V die opening

**Key:** v

**Type:** number

**Default:** 16

**Min:** 4

**Max:** 200

**Step:** 1

**Unit:** mm

**Help:** A common starting rule for air bending is 6 to 8 times the thickness.

#### Bend length

**Key:** len

**Type:** number

**Default:** 1000

**Min:** 10

**Max:** 6000

**Step:** 10

**Unit:** mm

#### Bending method

**Key:** mult

**Type:** select

**Default:** 1

**Options:**

##### Air bending

**Value:** 1

##### Bottoming (rough multiplier 3x)

**Value:** 3

##### Coining (rough multiplier 5x)

**Value:** 5

**Help:** Multipliers are rule-of-thumb values. Check the tooling maker's chart for exact numbers.

#### Machine capacity

**Key:** cap

**Type:** number

**Default:** 100

**Min:** 10

**Max:** 1000

**Step:** 5

**Unit:** tonnes

**Outputs:**

#### Bending force

**Key:** kn

**Expr:** 1.42 * uts * len * pow(t, 2) / v / 1000 * mult

**Format:** decimal

**Description:** Force in kilonewtons.

#### Bending force (metric tonnes-force)

**Key:** tonnes

**Expr:** kn / 9.80665

**Format:** decimal

**Primary:** true

#### Bending force (US short tons)

**Key:** us_tons

**Expr:** tonnes * 1.10231

**Format:** decimal

#### Tonnes per meter of bend

**Key:** tpm

**Expr:** tonnes / len * 1000

**Format:** decimal

#### Machine utilization

**Key:** util

**Expr:** tonnes / cap * 100

**Format:** percent

**Primary:** true

**Description:** Aim to stay well below the rated capacity, and below the tooling limit.

#### V opening / thickness

**Key:** vt

**Expr:** v / t

**Format:** decimal

#### Approx. minimum flange

**Key:** flange

**Expr:** 0.7 * v

**Format:** decimal

**Description:** Rule-of-thumb minimum flange length in mm for air bending.

**Chart:**

#### Tonnage vs thickness (V die held constant)

**Type:** line

**X:** t

**From:** 0.5

**To:** 6

**Steps:** 24

**Series:**

- tonnes

**Disclaimer:** This is an estimate based on the common air bending formula. Always confirm against the press manufacturer's and tooling maker's load charts, and never exceed the lowest rated capacity of the punch, die or machine.

## Content

**Intro:** Press brake tonnage depends on material strength, thickness squared, bend length and the width of the V die. This calculator estimates the force for air bending, bottoming or coining and compares it with the capacity of your machine.

**Sections:**

#### How to use the calculator

**Body:** Pick a material strength, enter the thickness, V die opening and bend length, and choose the bending method. The tool gives the force in kilonewtons, metric tonnes-force and US short tons, plus tonnes per meter and machine utilization. If utilization approaches or exceeds your safe working range, use a wider V die, bend in sections, use a lower-strength material option, or choose a larger machine. The chart shows how steeply tonnage rises as thickness increases.

**Bullets:**

- Use the real bend length in contact with the die, not the sheet width.
- Choose the V opening before anything else, since force falls as the V widens.
- Check tooling limits as well as machine capacity.

#### The formula and its limits

**Body:** For air bending the common formula is F (kN) = 1.42 x UTS (MPa) x L (mm) x T squared (mm) / (V (mm) x 1000), where V is the die opening. Thickness is squared, so doubling thickness roughly quadruples the force. Narrowing the V raises force and tightens the radius. Bottoming and coining need substantially more, and the multipliers here are rough guides. The result also varies with yield behavior, die radius, friction and sheet condition, so treat it as a planning estimate.

**Bullets:**

- Force scales with thickness squared.
- Force falls in inverse proportion to V width.
- Tooling manufacturers publish their own load limits per meter.

#### Worked example

**Body:** For 2 mm mild steel at 400 MPa, a 16 mm V die and a 1,000 mm bend, force is about 142 kN, which is roughly 14.5 tonnes. On a 100 tonne press that is about 14.5 percent utilization, comfortable for the machine, though the tooling rating per meter must still be checked. The approximate minimum flange for that V is about 11 mm. For 6 mm plate on the same V, thickness squared is nine times larger, so you would move to a V near 48 mm.

**Bullets:**

- Check the stroke and daylight for deep parts.
- Check that the punch is rated for the load per meter.

#### Common mistakes

**Body:** Using nominal thickness instead of measured thickness, forgetting that stainless and high-strength steels need much more force than mild steel, and choosing a V that is too narrow are the usual causes of overloaded tooling. Another is loading a short part at one end of a long machine, which concentrates force in a small area. Record the V die used for every job in the routing so that quoting, scheduling and the operator all work from the same tooling assumptions.

**Bullets:**

- Do not load short bends at the table edge.
- Do not exceed the tooling limit even if the machine can.

**Cta:** If routing data, tooling lists and press capacity live in different places, Netray can help bring them together inside your ERP. We can build this on private infrastructure.

**Faq:**

#### How many tonnes does a press brake need for 2 mm mild steel?

**Answer:** With a 16 mm V die and mild steel near 400 MPa, expect roughly 14 to 15 tonnes per meter for air bending, based on the standard formula. Actual numbers vary with the die, material lot and radius, so check the tooling chart.

#### What V die opening should I use?

**Answer:** For air bending, a V of about 6 to 8 times the material thickness is a common starting point, with wider openings for thicker plate. A wider V lowers force and gives a larger radius, but also raises the minimum flange length.

#### Why does stainless need more tonnage?

**Answer:** Because the formula scales with tensile strength. Stainless 304 is commonly around 50 percent stronger than mild steel in this calculation, so the same bend takes proportionally more force. It also springs back more, so overbending is typically needed.

#### Is this safe to rely on for tooling limits?

**Answer:** No. It is a planning estimate. The rated load of the punch and die, usually given in tonnes per meter, and the machine plate must be checked in the manufacturer's documentation before running a job.

## Search terms

press brake tonnage calculator, press brake force formula, bending force calculator, air bending tonnage chart, press brake capacity check, v die opening calculator, tonnage per meter press brake, sheet metal bending force

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