Ratio Calculator

What is a ratio calculator?

A ratio calculator simplifies a ratio like 6:8 to its lowest terms (3:4) and solves missing values when you scale a ratio up — for example, working out how much ingredient you need to keep a recipe or mix proportionally.

How this calculator works

• Enter two numbers and the tool reduces the ratio to simplest form by dividing both by their greatest common divisor.
• It reports the decimal form and the first number as a percentage of the second.
• In scale mode, enter a known scaled value for one side and it computes the matching value for the other.
• Simplification rounds to whole numbers when possible, so results like 3:4 stay clean.

How to use the result

1. Use the simplified ratio for recipes, mixing ratios, and aspect ratios — 6:8 and 3:4 are the same mix.
2. In scale mode, increase one part and get the exact value for the other — perfect for paint mixing, dough recipes, and concrete or fertilizer ratios.
3. Check the percentage form to express one part relative to the other in plain terms.
4. Verify scaled results in the real world by doubling small batches — ratios hold, but rounding in tools can drift on tiny amounts.

How do you simplify a ratio?

Divide both numbers by their greatest common divisor. For 6:8, the GCD is 2, giving 3:4. If both numbers are large or awkward decimals, the calculator handles the division; you can also scale decimals up to whole numbers first (0.5:0.75 → 50:75 → 2:3).

Common mistakes

• Reducing the wrong side. 3:4 and 4:3 are different ratios — keep the order straight when you enter values.
• Scaling one side only. To keep a ratio equal, both parts must scale by the same factor.
• Rounding too early. Round only at the end — intermediate rounding throws off scaled mixes.

Ratios are the proportional heart of many everyday numbers — the percentage calculator expresses the same relationship as a percent, and the unit converter handles the measurement conversions that ratios often sit on top of.