Welcome to the Math hub. Proportions are one of the most useful ideas in school mathematics — they connect ratios, fractions, percentages, scale drawings and algebra. Below are all of our free math proportion tools, each with a working calculator, a step-by-step guide and worked examples. No sign-up is needed, and every calculation runs in your browser.
Proportion Calculators and Guides
Proportion Calculator — Solve a/b = c/d for x, with an exact fraction, a decimal, steps and a cross-product check. Fractions, mixed numbers, decimals and negatives all work.
Ratio and Proportion — Learn what ratios and proportions are, how to simplify ratios, and how to test whether two ratios are proportional.
Proportional Relationship — Find the constant of proportionality k in y = kx, and use it to solve tables, graphs and word problems.
Direct and Inverse Proportion — Direct: y = kx. Inverse: xy = k. Learn to tell them apart and solve both kinds.
Percent Proportion — Solve part/whole = percent/100 to find the part, the percent or the whole, including discounts and tax.
Proportional Scale — Work with map scales, model scales and plans: find a drawing length, a real length or the scale 1:N.
Golden Proportion — The golden ratio φ = 1.618… in art, nature and design, with a golden rectangle calculator.
Proportions in School Math
In US 10th grade math, proportions appear in similar figures, scale drawings, percent problems and linear relationships. The skill is always the same: set up two equal ratios, cross-multiply, and solve. Master that one move and the rest — unit rates, scale factors, percent change — follows naturally. For the statistics side of proportions, including z-tests and confidence intervals, see the Statistics hub.
Math Hub FAQs
Which proportion tool should I start with?
Start with the Proportion Calculator on the homepage: it solves a/b = c/d for x and shows every step. Then read the Ratio and Proportion guide for the ideas behind it.
Are these math calculators free?
Yes — every calculator on this site is free, with no sign-up and no limits. All calculations run in your browser.