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Assembly Line Yield Loss Estimator

Estimate yield loss on an assembly line from total units processed and the number of good units produced. The calculator shows rejected or lost units, first-pass yield, and the percentage of input that did not become acceptable output during the measured period.

This view is useful when reviewing scrap, rework pressure, quality trends, or the output gap between gross production and saleable units. Enter counts from the same production window and use a consistent definition of “good” output so that comparisons between shifts, products, or improvement trials remain meaningful.

Inputs

units
units
Result
—
Calculated result
Good yield—
Lost / rejected output—
Total processed—

1. Define good output. Apply the quality acceptance rule used for the assembly line.

2. Enter total processed units. Use the gross count entering or completed by the measured process, according to your reporting convention.

3. Enter good units. Count output that meets the same acceptance rule in the same period.

4. Review yield loss. The main result shows the percentage not counted as good output.

5. Check both percentages and counts. Use the loss count for material or rework impact and the yield percentage for normalized comparisons.

Yield loss % = (total processed − good output) ÷ total processed × 100 Good yield % = good output ÷ total processed × 100

Total processed and good output must use the same counting basis and production window. The calculator treats every processed unit not counted as good output as a yield loss for the period.

What the result means

Use the result as an operational planning indicator for the defined production boundary and time period.

Actual production can differ when downtime, variability, quality rules, parallel resources, or product mix are handled differently from the assumptions entered here.

Given: total processed = 10,000 units; good output = 9,700 units.

Calculation: Lost output = 10,000 − 9,700 = 300 units. Yield loss = 300 ÷ 10,000 × 100 = 3.00%. Good yield = 9,700 ÷ 10,000 × 100 = 97.00%.

Result: Yield loss is 3.00%, representing 300 units not counted as good output.

Use the same classification rules across periods before interpreting a change as a true quality improvement or decline.

Should reworked output be counted as good?

Use the convention that matches your quality reporting objective. For first-pass yield, units needing rework are not good on the first pass; for final yield, successfully recovered output may be counted as good.

Can good output ever be greater than total processed?

No under a consistent counting boundary. The calculator flags that condition because it usually indicates mismatched periods, units, or counting definitions.

Is yield loss the same as scrap rate?

Not always. Yield loss can include any processed output not classified as good, while scrap rate may exclude items that can be reworked or recovered.

Why track the lost count as well as the percentage?

The percentage normalizes performance across different run sizes. The count helps quantify the physical volume affected by the loss.

Can I compare yield loss across different products?

Yes, but only cautiously. Different products may have different quality criteria, process complexity, and rework rules, so the underlying definitions should be aligned before comparing percentages.