How do I solve 3:4 = 9:x?

x = b × c ÷ a = 4 × 9 ÷ 3 = 12. Enter a, b and c and the working is shown with the answer.

How do I simplify 0.5:1.25?

Multiply both by 100 to get 50:125, then divide by the GCD 25 for 2:5. “Simplify a ratio” does both steps automatically.

How do I split 600 in the ratio 1:2:3?

The parts add to 6, so one share is 100 and the split is 100, 200 and 300.

If 1920×1080 is resized to 1280 wide, what is the height?

720. Enter the original size and the target width under “Scale proportionally”; the simplified 16:9 aspect ratio is shown too.

What is the difference between a ratio and a proportion?

A ratio compares quantities, written 3:4. A proportion is an equation saying two ratios are equal, 3:4 = 9:12. You simplify a ratio; you solve a proportion for its missing term.

How do I turn a ratio into a percentage?

Add the parts to get the whole, then divide each part by that total. In 1:2:3 the parts add to 6, so the shares are 16.7%, 33.3% and 50%.

What does 16:9 mean, and how do I get it from pixel dimensions?

It is the width-to-height ratio. Divide both dimensions by their greatest common divisor: 1920 and 1080 share a GCD of 120, which gives 16:9. Other common results are 4:3, 3:2, 16:10 and 21:9.

Can a ratio have more than two parts?

Yes. 1:2:3 is a three-part ratio and behaves the same way: simplify by dividing every part by the GCD, and divide a total by giving each part its share of the sum.

How do I scale a recipe or a mix up or down?

Keep the ratio and change the total. A 1:2 mix making 300 g is 100 g and 200 g; for 450 g it becomes 150 g and 300 g. Dividing a total in a ratio gives this directly.

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⚖️Ratio Calculator - Solve, Simplify, Share and Scale Proportionally

A ratio compares quantities — 3:4 means three of the first for every four of the second — and a proportion states that two ratios are equal, a:b = c:d. This calculator covers the four jobs that come up in practice. Solving a proportion finds the missing term by cross-multiplication: 3:4 = 9:x gives 3x = 4 × 9, so x = 12. Simplifying turns an awkward ratio into whole numbers by dividing every part by the greatest common divisor, scaling decimals up first, so 0.5:1.25 becomes 2:5, and each part is also shown as a percentage of the whole. Dividing a total works the other way round: add the parts to get the number of shares, divide the total by that, then multiply back — 600 split 1:2:3 is 6 shares of 100, giving 100, 200 and 300. Scaling keeps an aspect ratio fixed, since new height = old height × new width ÷ old width, which is why 1920×1080 resized to 1280 wide comes out at 720 and simplifies to 16:9. Every answer comes with the working, so it suits checking homework as much as sizing images, mixing paint or concrete, splitting a bill or reading a map scale.

Free · No sign-up · Runs in your browserLast updated: 2026-10-26

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How to use Ratio Calculator

1Choose the kind of ratio problem
2Enter the known values (ratios can be written 3:4 or 3:4:5)
3Read the answer together with the working

FAQ

How do I solve 3:4 = 9:x?: x = b × c ÷ a = 4 × 9 ÷ 3 = 12. Enter a, b and c and the working is shown with the answer.
How do I simplify 0.5:1.25?: Multiply both by 100 to get 50:125, then divide by the GCD 25 for 2:5. “Simplify a ratio” does both steps automatically.
How do I split 600 in the ratio 1:2:3?: The parts add to 6, so one share is 100 and the split is 100, 200 and 300.
If 1920×1080 is resized to 1280 wide, what is the height?: 720. Enter the original size and the target width under “Scale proportionally”; the simplified 16:9 aspect ratio is shown too.
What is the difference between a ratio and a proportion?: A ratio compares quantities, written 3:4. A proportion is an equation saying two ratios are equal, 3:4 = 9:12. You simplify a ratio; you solve a proportion for its missing term.
How do I turn a ratio into a percentage?: Add the parts to get the whole, then divide each part by that total. In 1:2:3 the parts add to 6, so the shares are 16.7%, 33.3% and 50%.
What does 16:9 mean, and how do I get it from pixel dimensions?: It is the width-to-height ratio. Divide both dimensions by their greatest common divisor: 1920 and 1080 share a GCD of 120, which gives 16:9. Other common results are 4:3, 3:2, 16:10 and 21:9.
Can a ratio have more than two parts?: Yes. 1:2:3 is a three-part ratio and behaves the same way: simplify by dividing every part by the GCD, and divide a total by giving each part its share of the sum.
How do I scale a recipe or a mix up or down?: Keep the ratio and change the total. A 1:2 mix making 300 g is 100 g and 200 g; for 450 g it becomes 150 g and 300 g. Dividing a total in a ratio gives this directly.