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

> Free online ratio calculator: solve a:b = c:x, reduce decimal ratios to whole numbers, divide a total in a given ratio, and scale sizes by ratio.

- URL: https://qilingtools.com/en/math/ratio
- Category: Math Tools (https://qilingtools.com/en/math)
- Tags: [Math](https://qilingtools.com/en/tags/math), [Education](https://qilingtools.com/en/tags/education)
- Last updated: 2026-10-26
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

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.

## How to use

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

## Features

- Solve a:b = c:x for the missing term
- Reduce decimal ratios to lowest whole-number terms, with each share as a percentage
- Divide a total in a ratio with any number of parts
- Scale sizes proportionally and show the simplified aspect ratio
- Working shown for every result

## 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.

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