Percent Nonconforming Calculator

Calculate percent nonconforming, total sample size, or units nonconforming when you enter any two values in a quality control sample.

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Percent Nonconforming Formula

The percent nonconforming calculation compares the number of nonconforming units to the total sample size. A nonconforming unit is a unit that does not meet the required specification or acceptance criteria.

PN = (N / S) * 100

• PN = percent nonconforming, as a percent
• N = total number of units nonconforming
• S = total sample size

To calculate the total number of nonconforming units, use:

N = (PN / 100) * S

To calculate the total sample size, use:

S = N / (PN / 100)

The calculator uses the same relationship in three ways:

• If you enter total sample size and total nonconforming units, it calculates percent nonconforming.
• If you enter percent nonconforming and total sample size, it calculates the number of nonconforming units.
• If you enter percent nonconforming and total nonconforming units, it calculates the total sample size.

Percent Nonconforming Reference Values

Use this table to see how different nonconforming counts affect the percent nonconforming for common sample sizes.

Example Calculations

Example 1: Calculate percent nonconforming

You inspect a sample of 200 units. Of those, 8 units are nonconforming.

PN = (8 / 200) * 100

PN = 4%

The percent nonconforming is 4%.

Example 2: Calculate nonconforming units

You have a sample size of 150 units and a percent nonconforming of 6%.

N = (6 / 100) * 150

N = 9

The total number of nonconforming units is 9.

FAQ

What does percent nonconforming mean?

Percent nonconforming is the percentage of inspected units that fail to meet the required standard. For example, if 3 units fail in a sample of 100, the percent nonconforming is 3%.

Is percent nonconforming the same as defect rate?

Not always. Percent nonconforming counts units that are nonconforming. A single unit may have one defect or many defects, but it is still counted as one nonconforming unit. Defect rate may count the total number of defects instead of the number of failed units.

Can the number of nonconforming units be a decimal?

In real inspections, the number of nonconforming units is usually a whole number. The calculator may return a decimal when solving from a percentage because it is doing a direct mathematical calculation. In practice, you may need to round to a whole unit based on your sampling method.