Metal Inspection Sampling Calculator

Determine inspection sample quantities from lot size using a selected percentage, minimum sample size, maximum sample size or fixed sampling plan.

Sampling Plan

Lot Size

Sampling Method

Sampling Percentage (%)

Minimum Sample Quantity

Maximum Sample Quantity

Rounding Method

Second-Stage Sample

This calculator converts the sampling rules you enter into a sample quantity. It does not select or certify a regulatory or industry sampling standard.

Ready to calculate. Press Calculate Inspection Sample.

Inspection Sample Estimate

Required First-Stage Sample
—

Lot Size

—

inspection units

Sampling Rate

—

of lot

Sample Ratio

—

of lot

Second Stage

—

additional units

Total Planned

—

sample units

Sampling Breakdown

Lot Calculation

Lot size
—

Raw percentage sample
—

Rounded sample
—

Minimum applied
—

Maximum applied
—

Sampling Plan

Selected method
—

First-stage sample
—

Second-stage sample
—

Total planned sample
—

Effective lot coverage
—

Sample Quantity by Lot Size

Lot Size	Raw Percentage Sample	Rounded Sample	Minimum / Maximum Applied	Lot Coverage

Percentage Sampling Formula

For percentage-based sampling, the raw sample quantity is calculated from the lot size and selected sampling percentage.

Raw Sample = Lot Size × Sampling Percentage ÷ 100

The selected rounding method then converts the raw result into a whole inspection unit.

Minimum and Maximum Controls

A minimum sample ensures that small lots do not produce an impractically small sample. A maximum sample can limit the calculated quantity for the user-selected planning method.

Adjusted Sample = Maximum(Minimum Sample, Rounded Percentage Sample)

When a maximum is enabled, the result is limited to the entered maximum quantity.

Fixed Sampling

The fixed sampling method bypasses percentage calculation and uses the quantity entered by the user.

First-Stage Sample = Fixed Sample Quantity

This is useful when a quality plan specifies a predetermined number of units to inspect from each lot.

Two-Stage Sampling

An optional second-stage quantity can be calculated from the first-stage sample or entered as a fixed quantity.

Second-Stage Sample = First-Stage Sample × Second-Stage Percentage ÷ 100

The second-stage value is an additional planning quantity and does not define acceptance or rejection criteria.

Important Limitations

This is a mathematical sampling calculator, not a standards-selection tool.
It does not determine acceptable quality limits.
It does not calculate acceptance or rejection numbers.
It does not determine statistical confidence or producer/consumer risk.
It does not automatically select an AQL or inspection level.
It does not automatically implement a specific national or international sampling standard.
It does not determine whether a lot is homogeneous.
Random selection of the actual inspection units must be planned separately.
Contractual specifications and quality plans may require a different sampling method.

Quality warning: Use the result only as a preliminary planning calculation unless the selected parameters have been established by the applicable inspection specification, contract, quality plan or engineering procedure.

Frequently Asked Questions

What does the Metal Inspection Sampling Calculator calculate?
It calculates a whole-number inspection sample from the lot size and sampling parameters entered by the user.

Can I calculate a percentage sample?
Yes. Enter the lot size and desired sampling percentage, then select the rounding method.

Can I set a minimum sample?
Yes. The minimum-sample option ensures that the calculated quantity does not fall below the entered minimum.

Can I set a maximum sample?
Yes. The percentage plus minimum plus maximum method limits the calculated sample to the entered maximum.

Can I use a fixed sample quantity?
Yes. Select Fixed sample quantity and enter the number of inspection units required.

Does this calculator follow a specific inspection standard?
No. It calculates according to the parameters you enter. If a contract, customer specification or applicable standard prescribes a sampling plan, use that plan's exact requirements.

Related Metal Inspection Tools

Corrosion Inspection Data Analyzer
Metal Remaining-Life Estimator
Rusted Metal Replacement Estimator
Metal Coating Thickness Converter
Dry Film Thickness Calculator