Ratio Calculator — Free Online Tool

Simplify any ratio to its lowest terms, explore equivalent ratios, and solve proportions — all computed instantly in your browser.

Simplifieda : b in lowest terms

enter values above and press Calculate

Proportion Solve a : b = c : x

x will appear here

x = (b × c) ÷ a — cross-multiply: a·x = b·c

Exact GCD simplification

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How it works

1Enter the two numbers of your ratio (decimals are fine).

2Press Calculate — both values are divided by their greatest common divisor.

3Use the proportion solver below to find a missing term.

Frequently asked questions

How is a ratio simplified?

Both numbers are divided by their greatest common divisor (GCD). For example, 12 : 18 has a GCD of 6, so it simplifies to 2 : 3. Decimal inputs are scaled up first (0.5 : 1.5 becomes 1 : 3).

What are equivalent ratios?

Equivalent ratios are found by multiplying or dividing both terms by the same number — the relationship stays identical. This tool shows ×2, ×3, and ÷2 (only when both terms are even integers, so no fractions appear).

How do I solve a proportion like 2:3 = 4:x?

Cross-multiply: 2·x = 3·4, so x = 12 ÷ 2 = 6. In general, x = (b × c) ÷ a. Enter a, b and c in the proportion solver above and press "Solve for x".

GCD-based simplification · Equivalent ratios · Proportion solver · 100% local — your numbers never leave this page.