Math calculators

Percent and Ratio Calculators

5 tools

Percentage, percent change, percent error, ratios, and proportions. Tools may appear in more than one topic.

Popular in Percent, Ratio & Proportion

Featured tools from the Family registry.

Percentage Calculator Calculate percentages, percentage of a number, and “what percent is X of Y” with clear arithmetic steps. Runs locally in your browser. Try it free.
Ratio Calculator Simplify ratios and scale quantities that stay in proportion. Runs locally in your browser. Free online tool — no sign-up. No account needed.

Every live calculator in this family. URLs stay /calc/math/…

Percent Error Calculator Compute percent error between experimental and accepted values for lab and measurement checks. Interactive calculations run locally; shared URLs and REST use the same engine. Free — no sign-up.
Percentage Calculator Calculate percentages, percentage of a number, and “what percent is X of Y” with clear arithmetic steps. Runs locally in your browser. Try it free.
Percentage Change Calculator Calculate the percentage increase or decrease from an initial value to a final value. You can also solve for the initial or final value. Free online — no sign-up.
Proportion Calculator Solve A:B = C:D for one missing term. Same engine as Ratio. Cross-multiply A·D = B·C. Not percent change. Not a second engine. Runs locally.
Ratio Calculator Simplify ratios and scale quantities that stay in proportion. Runs locally in your browser. Free online tool — no sign-up. No account needed.