Scrap Rate Calculator

Calculate manufacturing scrap rate and yield. This practical tool is an engineering estimate—validate decisions against machine, material, mold, and process data.

Formula and method

Scrap rate = scrap ÷ (good + scrap) × 100.

Inputs and units

Enter measured or specified values in the displayed units. Keep units consistent; results are rounded for practical planning. This first release uses the displayed engineering units rather than a unit-switcher.

Worked example

300 scrap ÷ (9,700 good + 300 scrap) × 100 = 3%.

Set a count rule before collecting data

Count good and scrap parts over the same time window and production definition. State how startup purge, runner recovery, rework, cavity defects, and customer rejects are handled so successive reports remain comparable.

Use yield to expose material and capacity loss

Send the resulting yield to material and output planning, then investigate the defect mechanism separately. A scrap percentage is an outcome, not a root-cause diagnosis.

Sanity check the denominator

Good plus scrap must describe the same production population. Mixing a weekly good count with a monthly scrap count makes the percentage meaningless.

Interpretation, assumptions, and limitations

This tool provides an estimate for planning and education. It does not replace machine maker limits, material data sheets, mold trials, cavity-pressure data, process validation, or qualified engineering review.

FAQ

Should recoverable runner be counted as scrap?

Use the site’s defined material-accounting rule and state it. Recoverable runner, unrecoverable startup waste, and rejected molded parts may need separate reporting.