PlantOps BI

KPI Library / Quality

Defect PPM (Parts Per Million)

Formula: (Defective units ÷ total units produced) × 1,000,000
Typical range: Automotive Tier 1 suppliers often target under 50 PPM; general manufacturing frequently runs in the hundreds to low thousands

Defect PPM expresses defect rate as defects per million units produced instead of a percentage, which makes small improvements visible at low defect rates where a percentage would round to zero. It’s the standard quality metric in automotive and electronics supply chains, where a customer scorecard will often name a specific PPM ceiling as a contract term.

What good looks like

Automotive Tier 1 suppliers commonly target under 50 PPM for shipped product, with the best programs running under 10. True Six Sigma (3.4 defects per million opportunities) is a statistical target almost nobody hits in practice across a full product line, and it’s frequently misquoted as a realistic near-term goal. General manufacturing outside automotive and electronics more often runs in the hundreds to low thousands of PPM, and that’s not automatically a problem if it’s stable and the customer’s spec doesn’t require better.

The undercounting trap is the one to watch. PPM calculated only from final inspection misses defects caught and reworked earlier in the process, which understates the true defect rate and hides the cost of rework. Decide up front whether PPM includes internal rework, customer returns, and field failures, or just shipped defects, and be consistent, because these three definitions produce very different numbers from the same process.

Defect PPM in Power BI (DAX)

With a production fact carrying units produced and defect units by part and shift:

Total Units =
SUM ( fact_production_hourly[units_produced] )

Defect Units =
SUM ( fact_production_hourly[defect_units] )

Defect PPM =
DIVIDE ( [Defect Units], [Total Units] ) * 1000000

Trend Defect PPM by defect code, not just as a single number. A plant chasing one aggregate PPM figure can spend months on the wrong root cause if the top three defect codes account for 80% of it and nobody’s looked.

Common mistakes

  1. Counting only final-inspection rejects. This undercounts true defect rate by excluding scrap and rework caught earlier in the process.
  2. Reclassifying rejects as rework to keep the reported PPM low. The unit still cost time and material; hiding it from PPM just moves the problem off the dashboard.
  3. Excluding customer returns and field failures from the calculation. Internal PPM can look great while the customer’s own scorecard, which counts what actually reaches them, tells a completely different story.