Post Stratification Calculator

Calculate post-stratification weights and weighted stratum totals from population and sample shares; flag strata with no sampled cases.

The Post Stratification Calculator compares each stratum's share of the population with its share of the sample. It reports the post-stratification weight and the sample count multiplied by that weight for every row.

Enter between 3 and 8 strata. Population values may be counts or proportional shares, but each stratum must use the same scale. A positive population share with no sampled cases cannot be weighted by this calculation.

Enter population counts or shares and sample counts for at least three strata.
Add or remove rows to match the strata in the population and sample.
Check that every positive-population stratum has sampled cases.
Review each stratum weight and weighted total.

Post-stratification weight

Weightₕ = (populationₕ / total population) / (sampleₕ / total sample).

Weighted totalₕ = sampleₕ × Weightₕ.

Reading post-stratification results

Weight and weighted total by stratum

A weight above 1 means the stratum's population share is larger than its sample share; a weight below 1 means it is smaller. The displayed weighted total is the entered sample count multiplied by that stratum's weight.

Statistics tips and best practices

Population counts and percentages both work because the formula uses shares; do not mix scales within one table.
Enter sample counts as whole numbers.
Resolve zero-sample strata before interpreting weighted totals.

Common mistakes to avoid

Mixing population counts and percentages in the same table.
Leaving a positive-population stratum with zero sampled units.
Reading a weight as a probability or as an estimated outcome.

This calculator computes weights from supplied stratum totals only. It does not apply those weights to survey responses or calculate uncertainty estimates.