Ratio & Proportion Calculator
Reduce a ratio to its simplest form, or solve a proportion like A:B = C:? for the missing value. It's a quick, private tool for recipes, scale drawings, mixes and side-by-side comparisons.
- 100% free
- Private & safe
- Runs in your browser
Why use Ratio Calculator?
Ratio Calculator gives you accurate results instantly, with the underlying formula shown so you can trust the numbers.
- Runs instantly in your browser — nothing to install, nothing uploaded.
- Completely free, with no account, no watermarks and no usage limits.
- Handles Simplify by dividing both sides by the greatest common divisor.; Proportion: A:B = C:x → x = B × C ÷ A.
- Enter the two parts of your ratio (A and B).
- Works on any device — desktop, tablet and phone — and is fully keyboard accessible.
How to use Ratio Calculator
- Enter the two parts of your ratio (A and B).
- See the simplified ratio and its decimal value.
- To solve a proportion, enter C in A:B = C:?.
- The missing value is calculated for you.
Examples
- Simplifying 16:9.
- Solving 3:4 = 9:? for a scaled recipe.
Formulas
- Simplify by dividing both sides by the greatest common divisor.
- Proportion: A:B = C:x → x = B × C ÷ A
Limitations
- Works with numeric ratios; three-part ratios must be simplified pairwise.
- Division by zero in a proportion is guarded.
Frequently asked questions
How does it simplify a ratio?
By dividing both numbers by their greatest common divisor.
Can it solve for a missing value?
Yes — enter C to solve A:B = C:? for the fourth term.
Does it handle three-part ratios?
Simplify them two numbers at a time using their common divisor.
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