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Ratio Calculator

Simplify ratios, solve proportions, and scale ratio values

Results are estimates for informational purposes only — not professional financial, medical, or legal advice. See how we build and verify our calculators.

Frequently Asked Questions

How do I simplify a ratio?

Divide both sides by the GCD (Greatest Common Divisor). For 12:8: GCD(12,8) = 4. Simplified: 3:2. You can also convert to fractions and simplify: 12/8 = 3/2, ratio 3:2.

How do I solve a proportion?

If a:b = c:d, then ad = bc (cross multiplication). Solve for the unknown: if 3:5 = x:20, then 5x = 60, x = 12. Or use equivalent fractions: 3/5 = x/20, x = 3 x 20/5 = 12.

What is a 1:2 ratio in practical terms?

A 1:2 ratio means for every 1 unit of A, there are 2 units of B. Total is 3 parts: A is 1/3 (33.3%), B is 2/3 (66.7%). In cooking: 1:2 water to flour means 1 cup water per 2 cups flour.

How do ratios relate to percentages?

In a ratio a:b, a is a/(a+b) x 100% of the total, and b is b/(a+b) x 100%. For ratio 3:1: a = 75%, b = 25%. Percentages and ratios are interchangeable — 75% = 3:1, 50% = 1:1.

What are common aspect ratios?

Screen/TV: 16:9 (widescreen HD), 4:3 (older TVs), 21:9 (ultrawide cinema). Photography: 3:2 (35mm film/DSLR), 4:3 (compact cameras), 1:1 (square). Architecture: golden ratio 1:1.618 (phi). Maps: scales like 1:100,000 (1cm = 1km).

Proportion Examples

Solving Proportions

If 5 apples cost $3, how much do 12 apples cost?
5/3 = 12/x → x = 12 x 3/5 = $7.20

Splitting by Ratio

Split $240 in ratio 3:5 between A and B:
Total parts = 8, each part = $30
A = 3 x $30 = $90, B = 5 x $30 = $150