Ratio Calculator
Work with ratios in three ways: simplify A:B, scale A:B to a target for A or B, or solve a proportion (A:B = C:D).
Simplify A:B
Privacy: calculations run locally in your browser. No inputs are stored or transmitted.
How it works
Simplify: divide A and B by their GCD (for integer ratios).
Scale: scale = target ÷ chosenSide, then A′ = A×scale, B′ = B×scale.
Proportion: A:B = C:D ⇒ A×D = B×C (cross multiplication).
Examples
- 10:15 → 2:3
- 2:3 scaled to A=10 → 10:15
- 2:3 = 10:D → D = 15
FAQ
- What is a ratio?
A ratio compares two quantities using division, often written as A:B or A/B.
- How do you simplify a ratio?
Divide both parts by their greatest common divisor (GCD). Example: 10:15 → 2:3.
- How do you scale a ratio to a target value?
Pick which side to target (A or B), compute scale = target ÷ currentSide, then multiply both sides by scale.
- What is a proportion (A:B = C:D)?
A proportion states two ratios are equal. You can solve for a missing value using cross multiplication.
- Can ratios use decimals?
Yes. This tool supports decimals and will also show an approximated simplified integer ratio when possible.
- What if one side is zero?
A ratio like 0:5 is valid. But 5:0 implies division by zero when interpreted as A/B, so some operations (like percent forms) are undefined.