How is supplier defect PPM calculated?

Defective units divided by units received, times one million. Forty-five rejects in 120,000 receipts is 375 PPM, the same as a 0.0375% defect rate with the decimal moved for readability.

Why does a PPM figure need an interval?

Because it is computed from a count, and counts vary. Forty-five events could have been 33 or 58 with the process unchanged, spanning roughly 265 to 485 PPM, so the bare 375 invites decisions against counting noise.

My supplier went from 250 to 375 PPM. Is that worse?

One period cannot say: 250 sits inside the 95% interval of a 45-event period, so both readings are consistent with an unchanged process. Pool several periods and ask again when the event count is larger.

Is PPM the same as DPMO?

No. PPM counts defective units per million received; DPMO counts defects per million opportunities, and a part with twenty checked characteristics has twenty opportunities. Supplier scorecards generally use unit PPM.

Supplier Quality, Development & Audits calculator

Supplier Defect PPM Calculator: The Rate and Its Interval

Turn a supplier's rejects into PPM and see how much of the number is real. The rate, its 95% interval, the gap to target and the critical share all come back together.

What this calculator does

Convert a reject count into PPM with its 95% interval, so no escalation rides on noise.

Formula used

Defect PPM = defective units ÷ units received × 1,000,000
95% count interval = defects ± 1.96 × √defects
Lower and upper bounds = (defects ∓ margin) ÷ units received × 1,000,000
Over or under target = defect PPM − contract PPM target

Inputs explained

Defective Units Rejected: Units judged nonconforming, from receiving rejects to attributed returns.
Total Units Received: Units actually received in the same window, not ordered.
Contract PPM Target: The rate the supplier agreement or scorecard expects.
Critical or Safety Rejects Within the Count: Rejects whose defect is critical or safety-related, a subset.

How to use the result

Best suited to checking a PPM target before escalating a supplier, judging whether an improvement is distinguishable from noise, keeping critical rejects out of the blended rate.
Supplier defects cluster in bursts, so the true uncertainty is wider than the Poisson interval shown. PPM counts what receiving found; escapes past inspection are invisible here.

Current U.S. benchmarks

U.S. manufacturing runs at 75.7% of capacity (Federal Reserve, Aug 2026). New factory orders are up 8.5% year over year (Census).

Common questions

How is supplier defect PPM calculated? Defective units divided by units received, times one million. Forty-five rejects in 120,000 receipts is 375 PPM, the same as a 0.0375% defect rate with the decimal moved for readability.
Why does a PPM figure need an interval? Because it is computed from a count, and counts vary. Forty-five events could have been 33 or 58 with the process unchanged, spanning roughly 265 to 485 PPM, so the bare 375 invites decisions against counting noise.
My supplier went from 250 to 375 PPM. Is that worse? One period cannot say: 250 sits inside the 95% interval of a 45-event period, so both readings are consistent with an unchanged process. Pool several periods and ask again when the event count is larger.
Is PPM the same as DPMO? No. PPM counts defective units per million received; DPMO counts defects per million opportunities, and a part with twenty checked characteristics has twenty opportunities. Supplier scorecards generally use unit PPM.

Related guides

Last reviewed 2026-10-01.