Ratios compare quantities. Use the solver to scale a recipe, resize an image without distortion or convert a map distance — or reduce a ratio like 1920:1080 to 16:9.
How to use the Ratio Calculator
- 1 Choose "Solve proportion" or "Simplify ratio".
- 2 Enter the known values.
- 3 The missing value or simplified ratio appears instantly.
Formula
A : B = C : X → X = B × C ÷ A Simplify A : B → (A ÷ gcd) : (B ÷ gcd)
Worked examples
Input: 1920 : 1080 = 1280 : X
Result: X = 720
Keeps the 16:9 aspect ratio
Input: 1920 : 1080
Result: 16 : 9
Greatest common divisor is 120
What is a proportion?
Two ratios are in proportion when they are equal: 2 : 3 = 4 : 6. Cross-multiplying gives 2 × 6 = 3 × 4, which is how the missing term is found: X = B × C ÷ A.
Everyday uses
- Cooking: a recipe for 4 needs 300 g flour — for 6 people, 4 : 300 = 6 : X gives 450 g.
- Design: keep an image's aspect ratio when resizing.
- Maps and models: convert between scale distances and real ones.
Frequently asked questions
How do I simplify a ratio?
Divide both numbers by their greatest common divisor. 24 : 36 → divide by 12 → 2 : 3.
Can ratios use decimals?
The proportion solver accepts decimals. Simplifying requires whole numbers — multiply decimals by 10, 100… first.
Is a ratio the same as a fraction?
Closely related: the ratio A : B corresponds to the fraction A/B, but ratios can compare more than two quantities.
Related tools
Percentage Calculator
Three calculators in one: find X% of a number, what percent one number is of another, and the percentage change between two values.
Percentage Increase Calculator
Increase a number by a percentage, or find the percentage increase between an original and a new value.
Percentage Decrease Calculator
Reduce a number by a percentage, or find the percentage decrease from an original value to a lower one.
Discount Calculator
See the sale price and how much you save, including stacked "extra % off" discounts.
Markup Calculator
Set a selling price from cost and markup, or work out the markup and margin of an existing price.
Profit Margin Calculator
Calculate gross profit, margin and markup from cost and revenue — or the price needed for a target margin.