Ratio Calculator

Simplify any ratio or solve a proportion in one click. Enter two numbers to reduce them to their simplest form (1920 and 1080 become 16:9), or solve A:B = C:X when one value is unknown.

Simplify a Ratio

Enter any two numbers and the ratio is reduced to its smallest whole-number form.

Solve a Proportion (A:B = C:X)

Fill in three values and the missing fourth value is calculated instantly.

How to Simplify a Ratio

Simplifying a ratio means dividing both numbers by the same value until they cannot be divided any further. The value to use is the greatest common divisor (GCD):

Take the two numbers, like 1920 and 1080.
Find the largest number that divides both evenly. For 1920 and 1080 that is 120.
Divide both sides: 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9, so the ratio is 16:9.

More examples: 1440:1080 → 4:3, 1000:1500 → 2:3, and 1280:1024 → 5:4. The simplified ratio describes the shape, no matter how large or small the actual numbers are.

How to Solve a Proportion

When two ratios are equal, like A:B = C:X, you can find the missing value with one formula: X = B × C ÷ A.

16:9 = 1920:X → X = 9 × 1920 ÷ 16 = 1080
If a 1080 x 1350 image needs to be 540 pixels wide: X = 1350 × 540 ÷ 1080 = 675, so the resized image is 540 x 675.

This is exactly how resizing works in design tools: the proportion stays locked, one dimension is chosen, and the other follows.

Ratio vs Aspect Ratio

A ratio compares any two numbers (like ingredients in a recipe or a map scale). An aspect ratio is simply a ratio applied to the width and height of an image, screen or video. This calculator handles both: simplify numbers, or solve proportions for any project.

If you are working with a common shape, jump straight to a dedicated tool:

Ratio Calculator FAQ

What is a ratio calculator?

A ratio calculator simplifies two numbers to their smallest whole-number form (1920:1080 becomes 16:9) or solves a proportion when one value is missing.

How do I simplify 1920:1080?

Both numbers divide by 120, so 1920:1080 simplifies to 16:9.

How do you solve a proportion?

Cross-multiply: if A:B = C:X, then X = B × C ÷ A. For 16:9 = 1920:X, X = 9 × 1920 ÷ 16 = 1080.

Is this the same as an aspect ratio calculator?

Yes, when the two numbers are width and height. For common shapes like 16:9 or 4:5, the dedicated aspect ratio calculators also convert pixel sizes.