Ratio calculator
Pick what you need: a missing term, the simplest ratio, a split of an amount or an aspect ratio. Results update as you type.
What you enter stays on this page and is not sent anywhere.
Fill in three boxes and leave the unknown one empty. It also works as the rule of three: if 3 kg cost 12, what do 5 kg cost?
- Missing term D
- 15
Product of the outer terms = product of the inner terms
Type the terms of a ratio. Decimals and fractions are turned into whole numbers first.
- Simplest ratio
- 2 : 3
- Multiply every term by 4 to clear the decimals and fractions:6 : 9
- Divide every term by their greatest common divisor, 3:2 : 3
| Term | Share | Per 1 of the first |
|---|---|---|
| 2 | 40% | 1 |
| 3 | 60% | 1.5 |
Share an amount, a cost or a quantity by a ratio. Rounding is spread so the parts add up to the total.
| Part | Ratio | Share | Amount |
|---|---|---|---|
| Part 1 | 3 | 60% | 600 |
| Part 2 | 2 | 40% | 400 |
Type a width and a height in pixels, centimeters or any unit to get the ratio, or tap a common ratio.
- Simplest ratio
- 16 : 9
- As a decimal
- 1.778 : 1
16:9 is used for TVs, monitors and most online video.
Resize, keeping the ratio
- New height
- 720
1,280 × 720
How to use it
- Pick a tab: proportion, simplify, split or aspect ratio.
- Type the numbers; decimals and fractions such as 1/3 work too.
- Read the result and the working below it.
Questions
How do you solve a proportion like 2 : 3 = 10 : x?
In a true proportion the product of the outer terms equals the product of the inner terms. So 2 × x = 3 × 10, which gives x = 30 ÷ 2 = 15. The same rule finds any one missing term.
How do you simplify a ratio with decimals?
First multiply every term by the same number to clear the decimals, then divide by their greatest common divisor. 1.5 : 2.25 times 4 is 6 : 9, and dividing by 3 gives 2 : 3.
How do you split an amount by a ratio?
Add the ratio terms, then give each part its term divided by that sum. For 1,000 at 3 : 2 the sum is 5, so the parts are 600 and 400. When the parts must be whole units, the leftover units go to the parts that lost the most in rounding, so the total still matches.
What aspect ratio is 1920 × 1080?
Divide both sides by their greatest common divisor, 120, and you get 16 : 9. Some monitors are sold as 21 : 9 although their pixels, such as 2560 × 1080, reduce to 64 : 27.
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