Everything is worked out in your browser and saved on this device for next time.
About the ratio calculator
A ratio compares two amounts, like 16 : 9 for a screen or 1 : 2 for rice and water. This calculator has three modes:
- Simplify a ratio — brings A : B down to the smallest whole numbers, like 1920 : 1080 → 16 : 9
- Find the missing value — solves A : B = C : ?, like 16 : 9 = 1920 : 1080
- Share an amount — splits a total in the ratio A : B, like 500 in 16 : 9 → 320 + 180
In every mode you also see the shares of the whole in percent and A ÷ B as a decimal. Decimals work too: 1.5 : 2 becomes 3 : 4.
Features
- Three modes — Simplify a ratio, Find the missing value or Share an amount
- Decimals work — 1.5 : 2 becomes 3 : 4
- Percent shares — how much of the whole each part is
- Ratio to 1 and decimal — see A : B as a ratio to 1 and as A ÷ B
- Quick ratios — tap 16 : 9, 4 : 3, 3 : 2, 1 : 2 or 21 : 9
- Live update — the result changes while you type
- Copy — copy the result with one click
- Private — it works in your browser, nothing is uploaded, and your numbers are saved on this device
How to use it
- Pick Simplify a ratio, Find the missing value or Share an amount
- Type the two parts in A and B, or tap a quick ratio: 16 : 9, 4 : 3, 3 : 2, 1 : 2, 21 : 9
- For the missing value, type the third number in C (so that A : B = C : ?)
- To share, type the total in Amount to share
- Press Copy to copy the result, or Start again to clear it
Example
The tool opens with A = 16 and B = 9.
- Simplify: 16 : 9 (it is already as small as it gets), or 1.7778 : 1
- Shares of the whole: 64 % / 36 %
- Find the missing value with C = 1920: 16 : 9 = 1920 : 1080
- Share an amount of 500: 320 + 180
Simplified ratios
| A : B | Simplest form | As a ratio to 1 | Shares |
|---|---|---|---|
| 1920 : 1080 | 16 : 9 | 1.7778 : 1 | 64 % / 36 % |
| 12 : 8 | 3 : 2 | 1.5 : 1 | 60 % / 40 % |
| 21 : 9 | 7 : 3 | 2.3333 : 1 | 70 % / 30 % |
| 1.5 : 2 | 3 : 4 | 0.75 : 1 | 42.86 % / 57.14 % |
| 4 : 3 | 4 : 3 | 1.3333 : 1 | 57.14 % / 42.86 % |
| 1 : 2 | 1 : 2 | 0.5 : 1 | 33.33 % / 66.67 % |
Screen sizes in 16 : 9
| Width | Height |
|---|---|
| 1280 | 720 |
| 1920 | 1080 |
| 3840 | 2160 |
How it works
- Simplify: divide A and B by their greatest common factor. 1920 and 1080 share 120, so 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9.
- Missing value: ? = C × B ÷ A. So 1920 × 9 ÷ 16 = 1080.
- Share: part A = total × A ÷ (A + B). So 500 × 16 ÷ 25 = 320, and the rest is 180.
Frequently asked questions
How do I simplify a ratio?
Find the biggest number that divides both parts (the GCF) and divide both by it. 12 : 8 ÷ 4 = 3 : 2.
How do I find the missing number in a proportion?
Multiply across and divide. In 16 : 9 = 1920 : ?, the answer is 1920 × 9 ÷ 16 = 1080.
How do I divide money in a ratio?
Add the parts of the ratio, divide the total by that sum, then multiply by each part. 120 in 2 : 3 gives 120 ÷ 5 = 24, so 48 and 72.
Can I use decimals?
Yes. The tool scales them up to whole numbers first, so 1.5 : 2 becomes 3 : 4.
What is an aspect ratio?
It is the width compared with the height of a screen, photo or video. 16 : 9 is the common widescreen shape, 4 : 3 is the older TV shape.
How do I turn a ratio into percentages?
Divide each part by the sum of the parts and multiply by 100. The tool shows this as shares of the whole.
Good to know
- Everything is worked out in your browser — nothing is sent anywhere
- Your numbers and mode are saved on this device for next time
- The tool works with two parts (A : B)
Related tools
- GCF and LCM Calculator — the greatest common factor behind simplifying
- Fraction Calculator — a ratio is also a fraction
- Percentage Calculator — more work with percentages
- Baking Converter — scale a recipe
- Unit Price Calculator — compare prices per unit
