How do you calculate false reject cost?

Multiply monthly volume by the false reject rate to get false-rejected parts, multiply by cost per part for variable cost, then add fixed sorting cost. With 50,000 parts, 2.5% false rejects, $4.80/part, and $800 fixed, total is $6,800/month.

What is a good false reject rate?

It depends on part value, but well-tuned vision lines often run false reject rates below 1%. At 2.5% on 50,000 parts, you're scrapping 1,250 good parts a month, a strong signal the threshold is too tight.

What does false reject cost per part mean?

It spreads the total monthly false reject cost across every inspected part. In the example, $6,800 over 50,000 parts is $0.136 per inspected part, a hidden cost you can compare against margin.

Why include a fixed sorting and containment cost?

False rejects usually trigger manual re-sort, containment, and re-inspection labor that doesn't scale neatly with volume. The example's $800 fixed cost lifts total from $6,000 variable to $6,800.

How do I reduce false reject cost?

Loosen overly tight thresholds, improve lighting and part presentation, retrain or recalibrate the algorithm, and add a confirmation re-inspection of rejected parts. Cutting the rate from 2.5% to 1% here would save roughly $2,880/month in variable cost.

False reject cost vs. missed defect cost: which matters more?

Both hurt: false rejects waste good parts and labor, while missed defects (false accepts) ship defects to customers. This calculator covers the false-reject side; you need to balance it against escape risk when setting thresholds.

Machine Vision & Industrial Inspection AI calculator

False Reject Cost Calculator

False reject cost quantifies the money lost when an inspection system scraps or pulls good parts it wrongly flags as defective. Quality and vision engineers use it to size the hidden tax of an over-tight inspection threshold or a poorly tuned algorithm. It matters because false rejects burn good material, trigger unnecessary sorting and containment, and inflate scrap rates without improving outgoing quality. This calculator converts a reject percentage into real monthly dollars and a per-part cost you can act on.

What this calculator does

Estimate the monthly cost of false rejects from a machine vision or automated inspection system, where good parts are incorrectly flagged as defective and removed from production.
Use it when optimizing pass-fail thresholds or camera parameters and you need to quantify what over-sensitivity is costing in scrapped or reworked good parts each month.
It computes total monthly false reject cost and cost per inspected part from volume, per-part cost, false reject rate, and fixed sorting cost.

Formula used

Monthly false rejects = monthly production volume x false reject rate / 100
Variable false reject cost = monthly false rejects x cost per part
Total monthly false reject cost = variable cost + fixed sorting and containment cost

Inputs explained

Monthly production volume inspected:
Cost per falsely rejected good part:
False reject rate (good parts wrongly rejected):
Fixed monthly sorting and containment cost:

How to use the result

Use it when tuning inspection thresholds, evaluating a new vision setup, or chasing an unexplained scrap spike.
It counts only false rejects of good parts; it does not value missed defects (false accepts) or downstream escape costs.

Common questions

How do you calculate false reject cost? Multiply monthly volume by the false reject rate to get false-rejected parts, multiply by cost per part for variable cost, then add fixed sorting cost. With 50,000 parts, 2.5% false rejects, $4.80/part, and $800 fixed, total is $6,800/month.
What is a good false reject rate? It depends on part value, but well-tuned vision lines often run false reject rates below 1%. At 2.5% on 50,000 parts, you're scrapping 1,250 good parts a month, a strong signal the threshold is too tight.
What does false reject cost per part mean? It spreads the total monthly false reject cost across every inspected part. In the example, $6,800 over 50,000 parts is $0.136 per inspected part, a hidden cost you can compare against margin.
Why include a fixed sorting and containment cost? False rejects usually trigger manual re-sort, containment, and re-inspection labor that doesn't scale neatly with volume. The example's $800 fixed cost lifts total from $6,000 variable to $6,800.
How do I reduce false reject cost? Loosen overly tight thresholds, improve lighting and part presentation, retrain or recalibrate the algorithm, and add a confirmation re-inspection of rejected parts. Cutting the rate from 2.5% to 1% here would save roughly $2,880/month in variable cost.

Last reviewed 2026-05-12.