Calculations

How to Calculate Supplier PPM, Audit Workload, and CAPA Cycle Time

The core supplier quality math worked in full: PPM, audit day workload, CAPA cycle time, and a weighted risk score, with real numbers and unit checks.

Defect PPM is the anchor metric. The formula is defects divided by units received, times 1,000,000. If incoming inspection rejects 47 parts out of a 62,000 piece shipment, that is 47 / 62,000 = 0.000758, times 1,000,000 = 758 PPM. Pull the numerator from your nonconformance log and the denominator from receiving records for the same period, not the same lot, or you will bias the rate. The Supplier Defect PPM calculator handles rolling 3 month and 12 month windows so a single bad lot does not swing a supplier from 200 PPM to 4,000 PPM on a monthly chart.

Audit workload converts a supplier list into auditor days. Take the number of suppliers in each risk tier, multiply by audit frequency per year, then by days per audit. Say you have 40 critical suppliers audited annually at 2.5 days each, plus 120 standard suppliers on a 3 year cycle at 1.5 days each. That is 40 x 1 x 2.5 = 100 days, plus 120 x 0.333 x 1.5 = 60 days, totaling 160 auditor days. Add 25 percent for travel and report writing and you need roughly 200 days, or one full time auditor plus a fraction. The Supplier Audit Workload calculator does this tiering automatically.

Corrective action cycle time measures how long a supplier takes to close a CAPA, from issuance to verified closure. Sum the calendar days for each closed 8D and divide by the count. If 12 CAPAs closed in a quarter with day counts summing to 546, mean cycle time is 546 / 12 = 45.5 days. Track the median too, because one 210 day zombie CAPA drags the mean. Feed dates straight from your quality system so you capture the verification step, not just the supplier's claimed fix date. The Supplier Corrective Action Cycle Time calculator separates response time from full closure time.

A weighted supplier risk score rolls several signals into one number. Assign weights that sum to 1.0, for example quality PPM 0.35, on time delivery 0.25, financial health 0.20, and audit findings 0.20. Normalize each input to a 0 to 100 scale where 100 is best, then take the weighted sum. A supplier at PPM score 60, delivery 90, financial 75, audit 50 scores 0.35(60) + 0.25(90) + 0.20(75) + 0.20(50) = 21 + 22.5 + 15 + 10 = 68.5. The Supplier Risk Score calculator lets you set weights and see the tier break at, say, 70 and 85.

PPAP review workload is easy to underestimate because reviews are lumpy. Estimate parts submitted per year, multiply by average hours per review by submission level. A Level 3 PPAP with an 18 element package runs 6 to 10 review hours; a Level 2 runs 2 to 4. If you expect 85 Level 3 packages at 8 hours and 140 Level 2 at 3 hours, that is 680 + 420 = 1,100 hours, or about 0.6 of a headcount at 1,800 productive hours per year. The PPAP Review Workload calculator converts submission mix into staffing directly.

Incoming inspection burden is a rate, not a raw count. Divide inspection hours by units received to get hours per thousand pieces, or express it as percent of receipts inspected. If you inspect 100 percent of 3 critical part numbers but skip lot sampling elsewhere, weight by volume. Suppose 220 inspection hours cover 480,000 received pieces: that is 0.46 hours per thousand. Cut it by moving proven suppliers to skip lot or dock to stock once they hold under 100 PPM for 6 consecutive lots. The Incoming Inspection Burden calculator ties this to your AQL sampling plan.

Unit discipline is what separates a defensible number from a guess. PPM is dimensionless per million, cycle time is calendar days not business days unless you state it, workload is auditor days or review hours, and burden is hours per unit volume. Always fix the time window first, then the population, then the count, in that order. If you compute PPM on units shipped but pull defects found at your dock, the two populations do not match and the rate is meaningless. Every one of these calculators asks for the window explicitly so the numerator and denominator align.

Published 2026-07-01.