Queendom Tools

Clamping Force Calculator: Tonnage from Area & Pressure

For tooling engineers sizing a press before a mold is cut, this gives a first-pass clamping tonnage from projected area and cavity pressure in seconds — so a 400 t machine is not quoted for a job that needs 650 t. This calculation helps estimate the required tonnage from a mold's projected area and cavity pressure using the formula F = P * A.

Injection Molding Clamping Tonnage

Intermediate Force (kN):
0.00
Required Tonnage (t):
0.00
t = (area cm² × pressure bar × 10) / 9806.65 × safety factor

Results are for preliminary estimation only — verify against the governing standard or a qualified professional.

How to Use This Calculator

  1. Enter the total projected area in cm² — every cavity plus the runner, measured perpendicular to the clamp direction.
  2. Enter the cavity pressure in bar for the material and wall section being run.
  3. Set the safety factor multiplier (start at 1.2 and adjust for your shop's practice).
  4. Read the required tonnage in tonnes and the intermediate force in kN, with the formula reproduced below the result.

FAQ

Q: What is the formula for injection molding clamping force?
A: Tonnage = (projected area in cm² × cavity pressure in bar × 10) / 9806.65 × safety factor, which is the estimate F = P × A expressed in tonnes.
Q: What projected area do I enter — one cavity or all of them?
A: The total projected area: sum every cavity's projected area and add the runner, since the clamp has to hold all of them at once.
Q: What cavity pressure should I use?
A: The pressure inside the cavity during fill and packing, in bar — not the machine's hydraulic pressure, which is a different number.
Q: Is this tonnage figure safe to order a machine from?
A: No — it is for preliminary estimation only and is not a substitute for review by a qualified/licensed engineer.