How do you calculate optical defect rate?

Divide rejected components by total inspected and multiply by 100. With 7 rejects out of 200 inspected, that is 7/200 x 100 = 3.5%.

What is a good optical defect rate?

For commodity optics, under 2-3% is typical; precision laser optics and coated windows often demand under 1% or are tracked in ppm. The default example at 3.5% sits 0.5 points above a 3% target, so it fails.

What does a negative gap to target mean?

A negative gap means you are below your maximum acceptable rate and passing. A positive gap, like the +0.5 in this example, means you exceeded the ceiling and the lot needs containment or rework.

Defect rate vs first-pass yield — what is the difference?

They are complements: a 3.5% defect rate corresponds to a 96.5% first-pass yield. Defect rate is the convention when you track failures and ppm; yield is the convention when you track good output.

Should I count cosmetic and functional defects together?

Track them separately, then combine for the headline rate. A scratch-dig cosmetic reject and a wavefront failure have different root causes and customer impact even though both increment the same total.

How many parts should I inspect for a reliable rate?

With only 200 parts, a single reject shifts the rate 0.5 points, so small lots are noisy. For a 1% target you generally want several hundred to a few thousand pieces before the rate is statistically trustworthy.

Lasers, Optics & Photonics Manufacturing calculator

Optical Defect Rate Calculator

Optical defect rate is the percentage of inspected components that fail spec — scratch-dig, coating pits, wavefront error, or surface figure out of tolerance. Quality engineers and line leads in precision optics and laser-component fabs track it per lot, per coating run, and per operator to catch process drift before a whole batch is scrapped. It is the single fastest read on whether your polishing, coating, or assembly process is in control. A rate that creeps above target usually signals contamination, a worn pad, or an unstable coating chamber long before yield collapses.

What this calculator does

Calculate optical component defect rate by comparing rejected units (scratch-dig failures, coating defects, dimensional non-conformances) to total units inspected, then measure the gap to your quality target.
Use this when monitoring quality on a production lot of lenses or mirrors, presenting defect trends at a quality review, or deciding whether a process change has improved surface quality.
It computes the share of inspected optics that were rejected and the gap between that rate and your maximum acceptable defect target.

Formula used

Optical defect rate = rejected components / total inspected x 100
Gap to target = optical defect rate - defect rate target

Inputs explained

Rejected optical components:
Total components inspected:
Defect rate target (maximum acceptable):

How to use the result

Use it at final inspection of any optics lot, after a coating or polishing run, or during process qualification to confirm a step holds spec.
A single rate hides defect type and root cause — a 3.5% rate from one bad coating run behaves very differently from 3.5% spread evenly across causes.

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).
Industrial electricity averages 8.66 cents per kWh across the U.S. (EIA, Apr 2026), up 5.5% from a year earlier. Energy-intensive steps carry this directly into unit cost.
The U.S. has 11,261 computer and electronic products establishments employing about 815,443 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate optical defect rate? Divide rejected components by total inspected and multiply by 100. With 7 rejects out of 200 inspected, that is 7/200 x 100 = 3.5%.
What is a good optical defect rate? For commodity optics, under 2-3% is typical; precision laser optics and coated windows often demand under 1% or are tracked in ppm. The default example at 3.5% sits 0.5 points above a 3% target, so it fails.
What does a negative gap to target mean? A negative gap means you are below your maximum acceptable rate and passing. A positive gap, like the +0.5 in this example, means you exceeded the ceiling and the lot needs containment or rework.
Defect rate vs first-pass yield — what is the difference? They are complements: a 3.5% defect rate corresponds to a 96.5% first-pass yield. Defect rate is the convention when you track failures and ppm; yield is the convention when you track good output.
Should I count cosmetic and functional defects together? Track them separately, then combine for the headline rate. A scratch-dig cosmetic reject and a wavefront failure have different root causes and customer impact even though both increment the same total.

Last reviewed 2026-05-12.