How do you calculate yield loss?

Divide rejected units by total units produced. With 8 rejected coils out of 250 wound, the yield-loss rate is 8 ÷ 250 = 3.2%.

What is a good yield-loss rate for coil winding?

Well-controlled winding lines run under 2-3% loss on established products. The 3.2% in this example is borderline — acceptable for a new build, but worth investigating on a mature part.

Yield loss vs first-pass yield — what's the difference?

Yield loss is the reject fraction; first-pass yield is its complement. A 3.2% yield loss equals a 96.8% first-pass yield on the same batch.

What does the gap-to-target number mean here?

It's the distance between your target and the calculated loss rate. With a 95% target and a 3.2% loss rate, the reported gap is 91.8 points, showing the loss rate is far under the target ceiling — you're comfortably inside goal.

How many coils should I sample before trusting the rate?

Rate stability improves with batch size. At 250 units the 3.2% figure is reasonably trustworthy; on runs under 50 units, treat any single-batch rate as directional only.

How do I reduce yield loss on a winding line?

Attack the top defect mode first — usually interlayer shorts, wrong turn count, or lead breakage. Turn-count verification and tension monitoring typically move the rate more than tightening final inspection.

Transformers, Coils & Magnetics Manufacturing calculator

Yield Loss Calculator

Yield Loss is the share of wound coils or magnetic assemblies that fail inspection and get scrapped or reworked in a batch. Quality engineers and winding-line leads in transformer and magnetics shops track it because interlayer shorts, turn-count errors, and lead-dress defects are expensive once copper and insulation are already committed. Knowing the exact loss rate — and how far it sits from your target — tells you whether a batch is drifting and whether a corrective action is worth stopping the line for. It converts a raw reject count into a percentage you can trend and compare across products.

What this calculator does

Yield Loss is the share of wound coils or magnetic assemblies that fail inspection and get scrapped or reworked in a batch.
Use it when yield loss in transformers, coils and magnetics manufacturing needs a clean rate and gap-to-target you can put on a tier board.
It computes the yield-loss rate by dividing rejected units by total units, and reports how many points that rate sits below your target yield.

Formula used

Yield Loss rate = affected amount ÷ total amount
Gap to target = target rate - calculated rate

Inputs explained

Coils rejected or reworked:
Total coils wound in batch:
Target first-pass yield:

How to use the result

Use it at batch close-out, during a first-article review, or whenever reject counts spike and you need to quantify the hit against a quality goal.
A single batch's rate is noisy on small runs — 8 rejects in 250 is meaningful, but 1 reject in 10 is not; always read the rate alongside sample size before reacting.

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 yield loss? Divide rejected units by total units produced. With 8 rejected coils out of 250 wound, the yield-loss rate is 8 ÷ 250 = 3.2%.
What is a good yield-loss rate for coil winding? Well-controlled winding lines run under 2-3% loss on established products. The 3.2% in this example is borderline — acceptable for a new build, but worth investigating on a mature part.
Yield loss vs first-pass yield — what's the difference? Yield loss is the reject fraction; first-pass yield is its complement. A 3.2% yield loss equals a 96.8% first-pass yield on the same batch.
What does the gap-to-target number mean here? It's the distance between your target and the calculated loss rate. With a 95% target and a 3.2% loss rate, the reported gap is 91.8 points, showing the loss rate is far under the target ceiling — you're comfortably inside goal.
How many coils should I sample before trusting the rate? Rate stability improves with batch size. At 250 units the 3.2% figure is reasonably trustworthy; on runs under 50 units, treat any single-batch rate as directional only.

Last reviewed 2026-05-12.