How do you calculate dimensional yield for magnets?

Divide the count of magnets within tolerance by the total gauged, then multiply by 100. With 8 in-tolerance out of 250 gauged, the dimensional yield is 3.2%.

What does the gap to target mean?

It is your yield minus the target yield, in percentage points. Against a 95% target, a 3.2% actual yield leaves a 91.8-point gap, signalling a process badly out of control rather than a minor trim.

What is a good dimensional yield for ground magnets?

Mature magnet grinding cells routinely run above 95% dimensional yield. A single-digit result like 3.2% almost always means a gauge, fixture or setup error rather than genuine part scatter.

Why is my dimensional yield so low all at once?

A sudden collapse usually points to a systematic cause: wrong gauge zero, a bad master, a fixture shift, or a sintering shrinkage change that moved every part the same way. Check the setup before assuming the parts are bad.

Should I gauge every magnet or a sample?

A representative sample sizes the yield, but for tight-tolerance rotor magnets many shops gauge 100% because a single out-of-print piece can stall a motor build.

How is dimensional yield different from overall lot yield?

Dimensional yield only counts pieces failing size tolerance after grinding. Overall yield also nets out magnetic, cosmetic and coating rejects, so it is always equal to or lower than dimensional yield.

Rare Earth Magnet & Motor Materials calculator

Dimensional Yield Calculator

Sintered NdFeB and SmCo magnets shrink and distort during sintering and must be ground to final dimension, so dimensional yield, the share of pieces that gauge within print tolerance, directly drives grinding cost and scrap. This calculator divides the count of in-tolerance magnets by the total gauged in the lot and compares the result against your target yield. Quality engineers and grinding-cell supervisors use it to catch a drifting press, worn grinding wheels, or a sintering shrinkage shift before a lot is scrapped. Because magnet grinding removes brittle, hard-to-rework material, a yield miss caught early is far cheaper than one found at final inspection.

What this calculator does

Estimate dimensional yield for rare earth magnet and motor materials using production-ready inputs so teams can track KPI performance and decide whether corrective action is needed.
Use it when dimensional yield in rare earth magnet and motor materials needs a clean rate and gap-to-target you can put on a tier board.
It computes the dimensional yield rate as in-tolerance count over total gauged, then reports the gap in points to your target yield.

Formula used

Dimensional yield rate = dimensional yield count ÷ total dimensional yield population × 100
Dimensional yield gap to target = dimensional yield rate - target dimensional yield rate

Inputs explained

Magnets within dimensional tolerance:
Magnets gauged in the lot:
Target dimensional yield rate:

How to use the result

Use it on a gauged sample or full lot after grinding to confirm the cell is holding tolerance before release.
It is a pass/fail count and does not tell you which dimension failed or by how much, so pair it with actual measurement data for root cause.

Current U.S. benchmarks

The producer price index for copper and brass mill shapes stands at 559.593 (BLS, May 2026), up 76.8% from a year earlier. Quotes priced off last quarter's material cost miss this move. Global copper trades at $13,484 per tonne (IMF via FRED, May 2026).
The U.S. has 5,397 electrical equipment and appliances establishments employing about 369,437 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate dimensional yield for magnets? Divide the count of magnets within tolerance by the total gauged, then multiply by 100. With 8 in-tolerance out of 250 gauged, the dimensional yield is 3.2%.
What does the gap to target mean? It is your yield minus the target yield, in percentage points. Against a 95% target, a 3.2% actual yield leaves a 91.8-point gap, signalling a process badly out of control rather than a minor trim.
What is a good dimensional yield for ground magnets? Mature magnet grinding cells routinely run above 95% dimensional yield. A single-digit result like 3.2% almost always means a gauge, fixture or setup error rather than genuine part scatter.
Why is my dimensional yield so low all at once? A sudden collapse usually points to a systematic cause: wrong gauge zero, a bad master, a fixture shift, or a sintering shrinkage change that moved every part the same way. Check the setup before assuming the parts are bad.
Should I gauge every magnet or a sample? A representative sample sizes the yield, but for tight-tolerance rotor magnets many shops gauge 100% because a single out-of-print piece can stall a motor build.

Last reviewed 2026-05-12.