Casting Shrinkage Calculator

Work out casting shrinkage instantly with clear inputs, formula shown and shareable results.

About Casting Shrinkage Calculator

Metal contracts as it solidifies and cools, so the pattern must be made larger than the finished casting by the linear shrinkage allowance: about 1 percent for grey iron, 2 percent for steel and 1.3 percent for aluminium. Volumetric shrinkage is roughly three times the linear figure, which is what the risers must feed.

Formulas

Pattern size

Pattern = casting dimension x (1 + linear shrinkage)

Volumetric

Volume shrinkage = (1 + linear)³ - 1

Worked example

With the default values below, Casting Shrinkage Calculator returns Pattern dimension of 204.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Required casting dimensionminimum 0.1 mm: 200 mm
Linear shrinkage allowanceaccepts 0.1–10 %: 2 %
Machining allowanceminimum 0 mm: 3 mm

Results

Pattern dimension: 204.00 mm
Shrinkage allowance: 4.00 mm
Pattern with machining allowance: 207.06 mm
Approximate volumetric shrinkage: 6.12% %

Step by step

1Values used
2Pattern size
3Volumetric
4Pattern dimension= 204.00 mm
5Shrinkage allowance= 4.00 mm
6Pattern with machining allowance= 207.06 mm
7Approximate volumetric shrinkage= 6.12 %

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Casting Shrinkage figure worked out?

Pattern = casting dimension x (1 + linear shrinkage). Metal contracts as it solidifies and cools, so the pattern must be made larger than the finished casting by the linear shrinkage allowance: about 1 percent for grey iron, 2 percent for steel and 1.3 percent for aluminium.

Is machining allowance added before or after shrinkage?

Add it to the casting dimension first, then apply shrinkage to the total, so the as-cast surface has enough metal to machine away after it has contracted.

What values do I need to enter?

This calculator takes 3 inputs: Required casting dimension, Linear shrinkage allowance, Machining allowance. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.