How this calculator works
Turn each percentage into a fraction and multiply. This describes a share within a share, such as the fraction of a group who belong to a subgroup. Applying the result to the original amount gives the final subset. It is different from two successive percentage increases, which multiply by 1 plus each rate.
Formula
Combined fraction c = p × q. Combined percentage number = P × Q / 100. Missing factor p = c/q when q ≠ 0.
Worked example
Twenty percent of 30% is 6% of the whole. Starting with 500, taking 20% leaves a share of 100; taking 30% of that share gives 30.
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Frequently asked questions
Do I add the two percentages?
No. Taking a percentage of another percentage multiplies the fractions.
Is this the same as two discounts?
For discounts, multiply the remaining fractions. A 20% discount followed by 30% off leaves 0.8 × 0.7 = 56% of the original price.
Why cannot I reverse a zero factor?
A zero product with a known zero factor has infinitely many possible missing factors. A non-zero product with a zero factor is impossible.