Injection Molding Clamp Tonnage Calculator

Calculate required clamping force for injection molding from projected part area, cavity pressure, number of cavities, and runner system.

Inputs

Part length (mm)

Part width (mm)

Cavity pressure (bar)

Number of cavities

Safety factor

Runner area (%)

Tab to move between fields

Results

Clamp force (metric tonnes)

63.5

Clamp force (US tons)70

Clamp force (kN)623

Total projected area (cm²)165

Runner area (cm²)15

Specific tonnage (t/cm²)0.39

Recommended machine (tonnes)80

How to Use This Calculator

Enter Part length (mm), Part width (mm), and Cavity pressure (bar).
Set Number of cavities, Safety factor, and Runner area (%).
Review the Clamp force (metric tonnes) result.
Use Clamp force (US tons) and Clamp force (kN) to inform your decision.

How the result changes with Part length (mm)

Part length (mm)	Clamp force (metric tonnes)
501	212.2
1,751	741.5
3,250	1,376.4
4,500	1,905.8

What each input means

Part length (mm): Length of the part in the parting-plane direction.
Part width (mm): Width of the part in the parting-plane direction.
Cavity pressure (bar): Average cavity pressure. PE/PP: 200-400, ABS: 300-600, PC: 400-700 bar.
Number of cavities: Number of identical cavities in the mold.
Safety factor: Typically 1.05-1.20 to account for process variation.
Runner area (%): Runner projected area as percentage of total part area. Hot runner = 0%.

What each result means

Clamp force (metric tonnes): Required clamping force in metric tonnes.
Clamp force (US tons): Required clamping force in US short tons.
Clamp force (kN): Required clamping force in kilonewtons.
Total projected area (cm²): Combined projected area of all cavities plus runners.
Runner area (cm²): Estimated projected area of the runner system.
Specific tonnage (t/cm²): Clamp force per unit projected area.
Recommended machine (tonnes): Next standard machine size above required clamp force.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Part length (mm) = 150, Part width (mm) = 100, Cavity pressure (bar) = 350, Number of cavities = 1 = 6 input(s) provided
Calculate Clamp force
Clamp force = clampForceKgf / 1000
63.5 = 63.5
Calculate Clamp force
Clamp force = clampForceTonnes * 1.10231
70 = 70
Calculate Clamp force
Clamp force = clampForceTonnes * 9.80665
623 = 623

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