Ratio Calculator

Simplify a ratio and scale it up or down.

How to simplify and scale a ratio

• Simplify: divide both numbers by their greatest common divisor. For 12 : 8, the divisor is 4, so the ratio becomes 3 : 2.
• Scale: keep the same proportion. If A is C, then B = C × B ÷ A.

Worked examples

• 12 : 8 simplifies to 3 : 2. If A is 30, B is 30 × 8 ÷ 12 = 20.
• Recipe: a mix uses 2 cups of flour for every 1 cup of sugar (2 : 1). With 5 cups of flour, you need 2.5 cups of sugar.
• Screens: 1920 × 1080 pixels simplifies to 16 : 9, because both numbers divide by 120.

Frequently asked questions

What is a ratio?

A ratio compares two quantities. 3 : 2 means that for every 3 of the first, there are 2 of the second.

What are equivalent ratios?

Ratios that describe the same proportion, such as 3 : 2, 6 : 4 and 30 : 20. Multiply or divide both parts by the same number to get them.

How is a ratio different from a fraction?

A fraction compares a part to a whole. A ratio compares any two quantities, which may both be parts.

Can I use decimals?

Yes, but simplifying works with whole numbers. With decimals, the calculator shows A ÷ B instead, and scaling still works.