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PPM Defective Calculator: Formula, Example & Instant Result

PPM (parts per million) defective expresses how many defective units there would be in one million produced or shipped. It is the same information as a percent defective, on a scale that makes small rates easy to compare: 0.1 % is 1,000 PPM.

↳ Values are pre-filled with an example — replace them with your own data.

Your data

parts
parts

Shipped, inspected or used — say which in your report.

Result

PPM defective2,960

About 2,960 defective units in every million.

Percent defective0.296%

Share of units that are defective.

Defective per 1,000 units2.96

At this rate, about 3.0 of every 1,000 units are defective.

1,000 squares; the red ones show about 3.0 defective units in every 1,000.

Formula

PPM = (defective units / total units) × 1,000,000
Defect rate % = (defective units / total units) × 100
1 % = 10,000 PPM; 0.1 % = 1,000 PPM; 0.01 % = 100 PPM

Worked example

A supplier shipped 12,500 molded housings last quarter; your incoming inspection and the line found 37 defective. What is the PPM?

Data

  • • Defective units = 37
  • • Total units shipped = 12,500

Step by step

  1. 1Defect rate = 37 / 12,500 = 0.00296
  2. 2PPM = 0.00296 × 1,000,000 = 2,960 PPM
  3. 3Percent defective = 0.00296 × 100 = 0.296 %
  4. 4Per 1,000 units: 0.00296 × 1,000 ≈ 3 units

What it means

The supplier is running at 2,960 PPM — roughly 3 defective housings in every 1,000 delivered. That is the figure to put in the supplier scorecard and to compare against the agreed PPM target.

Tips & common mistakes

  • State the population: PPM of shipped parts, of parts inspected, or of parts used on the line are different numbers.
  • With a small sample, one defect swings PPM a lot — 1 defect in 500 is already 2,000 PPM. Report the sample size too.
  • Count defective units, not defects: a part with two defects counts once. For defects per opportunity, use DPMO.
  • Zero defects in a sample does not mean 0 PPM in the population; it only bounds it.
  • AI assistants often slip a factor of 100 between percent and PPM — check the result against the conversion line in the formula box.

AI prompt for this calculation

Paste it into your AI assistant to be walked through the calculation with your own data.

Act as a supplier quality engineer and help me calculate PPM defective.

Use exactly these formulas:
PPM = (defective units / total units) × 1,000,000
Defect rate % = (defective units / total units) × 100

Rules:
1. Work step by step and show the rate as a decimal, a percentage and in PPM.
2. Repeat my counts first and check the thousands separators.
3. If the number of defective or total units is missing or unclear, ask me — never estimate it.
4. Tell me whether my count is defective units or defects; if it is defects, point me to DPMO instead.
5. If the sample is small (under a few thousand units), remind me that the PPM estimate is uncertain.

My data:
Defective units = 
Total units = 
What population this is (shipped / inspected / used) =

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<iframe src="https://www.qualityforeveryone.com/embed/calculators/en/ppm-defective-calculator" title="PPM Defective — Quality for Everyone" width="100%" height="1100" style="border:0;max-width:100%" loading="lazy"></iframe>
<p><a href="https://www.qualityforeveryone.com/en/lab/calculators/ppm-defective-calculator">PPM Defective calculator by Quality for Everyone</a></p>

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Frequently asked questions

What is the difference between PPM and DPMO?

PPM counts defective units per million units; DPMO counts defects per million opportunities. A unit with three possible defects can contribute up to three defects to DPMO but only one defective unit to PPM.

How do I convert PPM to percent and back?

Divide PPM by 10,000 to get percent (2,960 PPM = 0.296 %), and multiply a percentage by 10,000 to get PPM (0.5 % = 5,000 PPM).

What is a good PPM?

It depends entirely on the industry, the part and the contract. Targets in supplier agreements range from a few PPM to several thousand; any single figure quoted as 'good' is illustrative. Use the target agreed with your customer.

Can I calculate PPM from a sample instead of the whole population?

Yes, as an estimate. The smaller the sample, the wider the uncertainty: with few defects the true rate can be several times higher or lower than the sample PPM, so always report the sample size alongside it.

Last tested: October 2026 · Tested with: automated math tests (3+ cases) · Reviewed by: Quality for Everyone editorial team