How do you calculate shrinkage allowance in powder metallurgy?

Subtract the sintered dimension from the green dimension to get the absolute allowance, then divide by a reference dimension. With a green value of 125 and a sintered value of 100 against a reference of 100, the allowance is 25 units, or 25%.

What is a typical sintering shrinkage percentage?

Most iron- and steel-based structural PM parts shrink 0.5-2.5% linearly. Copper and some bronze systems can grow slightly. The 25% figure in the default example is illustrative of the math, not a typical structural-part shrinkage.

Why do I size the die larger than the finished part?

Because the part shrinks during sintering, the compacted green part must be larger than the final target by the shrinkage allowance. You cut the die to the green dimension so the sintered part lands on the finished spec.

Does green density affect shrinkage?

Strongly. Lower green density parts have more porosity to close, so they shrink more during sintering. That is why shrinkage allowance must be tied to a fixed pressing pressure and green density, not just the alloy.

Is shrinkage the same in every direction?

No. PM parts typically shrink less in the pressing direction than transverse to it because of density gradients. Critical features in different orientations may each need their own allowance rather than one global percentage.

How do I convert shrinkage percent into an oversize factor for the die?

An oversize factor equals green divided by sintered dimension. A 25% allowance on a 100-unit target means the die feature is cut to 125 units, a factor of 1.25.

Powder Metallurgy & Sintered Parts calculator

Shrinkage Allowance Calculator

Shrinkage allowance is the dimensional gap a powder metallurgy part loses (or, for some alloys, gains) as it densifies during sintering, and it is the number that decides how big the compaction die and core rods must be cut. Tool designers and PM process engineers live and die by it: cut the die to the finished dimension and every part comes out undersized. Because sintering shrinkage runs from a fraction of a percent up to several percent depending on powder, green density, and sinter temperature, getting this allowance right is the difference between a die that holds tolerance for a million parts and one that has to be reworked before first-article approval. This calculator expresses the allowance both as an absolute amount and as a percentage of a reference dimension so it scales across feature sizes.

What this calculator does

Shrinkage allowance is the dimensional gap a powder metallurgy part loses (or, for some alloys, gains) as it densifies during sintering, and it is the number that decides how big the compaction die and core rods must be cut.
Use it when shrinkage allowance in powder metallurgy and sintered parts needs a clean margin number for a powder metallurgy and sintered parts go / no-go review.
It computes the absolute dimensional allowance between a green and a sintered dimension, and expresses that allowance as a percentage of a chosen reference dimension.

Formula used

Shrinkage Allowance margin = available value - required value
Margin percent = margin ÷ reference value

Inputs explained

Green (as-pressed) dimension:
Sintered (final) target dimension:
Reference dimension for percentage:

How to use the result

Use it when sizing compaction tooling, setting up SPC on a critical feature, or converting a measured shrinkage into an oversize factor for the die.
It assumes uniform, isotropic shrinkage; real PM parts shrink anisotropically (differently in the press direction versus transverse), so a single allowance won't hold for every feature on a complex part.

Current U.S. benchmarks

The producer price index for steel mill products stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. Quotes priced off last quarter's material cost miss this move.
U.S. iron and steel imports ran $2.1B in May 2026 (Census International Trade). The U.S. ran a trade deficit of $0.4B in the category that month. Import volumes are the pressure gauge behind tariff and reshoring decisions.

Common questions

How do you calculate shrinkage allowance in powder metallurgy? Subtract the sintered dimension from the green dimension to get the absolute allowance, then divide by a reference dimension. With a green value of 125 and a sintered value of 100 against a reference of 100, the allowance is 25 units, or 25%.
What is a typical sintering shrinkage percentage? Most iron- and steel-based structural PM parts shrink 0.5-2.5% linearly. Copper and some bronze systems can grow slightly. The 25% figure in the default example is illustrative of the math, not a typical structural-part shrinkage.
Why do I size the die larger than the finished part? Because the part shrinks during sintering, the compacted green part must be larger than the final target by the shrinkage allowance. You cut the die to the green dimension so the sintered part lands on the finished spec.
Does green density affect shrinkage? Strongly. Lower green density parts have more porosity to close, so they shrink more during sintering. That is why shrinkage allowance must be tied to a fixed pressing pressure and green density, not just the alloy.
Is shrinkage the same in every direction? No. PM parts typically shrink less in the pressing direction than transverse to it because of density gradients. Critical features in different orientations may each need their own allowance rather than one global percentage.

Last reviewed 2026-05-12.