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CNC Machine Yield Loss Estimator

This CNC Machine Yield Loss Estimator translates a total production quantity and reject rate into estimated rejected parts, good parts, and yield. It helps manufacturing teams quantify the material and capacity impact of scrap or nonconforming output without mixing the result with downtime or speed losses.

The calculator is useful for batch reviews, quality planning, and simple what-if analysis. A lower reject rate increases good output even when the machine runs for exactly the same time, so the result can be paired with throughput or OEE analysis to understand where improvement effort may have the greatest operational effect.

Yield inputs

parts
%
Result
—
estimated rejected parts
Estimated good parts—
Yield—
Reject rate—

1. Enter total production
Use the total number of CNC parts produced in the batch, shift, or period being reviewed, including accepted and rejected pieces.

2. Enter reject rate
Provide the percentage of produced parts that are scrapped or otherwise classified as rejects under your quality rules.

3. Check rejected quantity
The main result estimates how many parts are lost at that reject rate.

4. Compare good output
Review the estimated good-part count and yield percentage to see the usable output remaining.

5. Test improvement scenarios
Reduce the reject rate while keeping total production constant to estimate how many additional good parts could be recovered.

Rejected parts = Total parts produced × Reject rate
Good parts = Total parts produced − Rejected parts
Yield = 100% − Reject rate

What the result means

The main result estimates the quantity of produced parts lost to the entered reject rate.

The estimator treats every rejected part equally and does not calculate financial loss. Reworkable parts should be classified consistently with your own reporting method.

Given: 2,400 machined parts and a 2.75% reject rate.

Calculation: Rejected parts = 2,400 × 0.0275 = 66. Good parts = 2,400 − 66 = 2,334. Yield = 97.25%.

Result: 66 rejected parts and 2,334 good parts.

This indicates that improving the reject rate would raise sellable output without requiring additional machine cycles.

Should reworked parts count as rejects?

Use the same definition your operation uses for yield reporting. If a reworked part eventually counts as good output, separating scrap from rework may give a clearer view.

Can I enter a reject rate measured from a sample?

Yes, but the result will be an estimate for the larger production quantity. Sampling uncertainty is not modeled by this calculator.

What happens at a 0% reject rate?

Estimated rejected parts become zero and yield becomes 100%.

Does this calculator include downtime losses?

No. It isolates quality loss from rejected output; downtime and speed losses belong in throughput or OEE analysis.

How can I estimate recovered output from a quality project?

Run the calculator at the current reject rate and again at the proposed lower rate. The difference in good parts is the estimated recovered output for the same total production quantity.