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Understanding Percentages

By Calculator Atlas editorial (draft)Publication date pending4 min read

A complete guide to percentages with formulas and everyday uses.

What is a percentage?

A percentage expresses a number as a fraction of 100. 25% means 25 out of every 100, or 0.25.

Finding a percentage of a number

Multiply the number by the percentage divided by 100.

  • Result = value × percent ÷ 100

Percentage change

Percentage change compares a new value to an old one.

  • Change % = (new − old) ÷ old × 100

Worked example

15% of 200 is 200 × 15 ÷ 100 = 30.

Sources

OpenStax, Prealgebra 2e. Percents: converting between fractions, decimals and percents, and percent change. Book-level citation; not checked against a specific section.