Aspect Ratio Calculator
Simplify a width and height to a ratio, see the nearest common one, and work out the other side of a size for the ratio you want to keep.
To make a picture this size, use the Image Resizer; to cut it to this shape, use Crop Image. Worked out on your device; nothing is sent or saved.
Aspect ratios, simplified and kept
An aspect ratio is the shape of a picture or screen: its width compared with its height. It matters when a video, slide or banner has to fit a space, or when you resize something and don’t want it squashed. This calculator finds the ratio of any size, and works out a missing width or height for the ratio you want to keep.
How to use it
- To find a ratio, type a width and a height: 1920 × 1080 gives 16:9.
- To keep a ratio, pick a preset or type your own, such as 3:2, or an original size such as 1366 and 768.
- Type the new width or the new height, and read the other side in whole pixels.
- Use the size in the Image Resizer or Crop Image.
What the results mean
- Simplified ratio: both sides divided by their greatest common divisor, so 1920 × 1080 becomes 16:9. Decimals work too: 8.5 × 11 is 17:22.
- Decimal ratio: the width divided by the height, such as 1.778:1, handy for comparing shapes.
- Nearest common ratio: when a size isn’t an exact match, the tool names the closest of 1:1, 5:4, 4:3, 3:2, 16:10, 16:9, 2:1 and 21:9 (or the same shapes upright) and says how far off it is. 1366 × 768 is 683:384, which is 0.05% wider than 16:9.
Rounding to whole pixels
Pixels come in whole numbers, but a ratio doesn’t always divide evenly. A 16:9 picture 1000 pixels wide would be 562.5 pixels tall, so the tool gives 563, says that it rounded, and suggests the nearest sizes that fit exactly: 992 × 558 or 1008 × 567. For 16:9, any width that’s a multiple of 16 gives a whole-number height.
Good to know
- 21:9 is the same shape as 7:3. A size near it may not be exact: 2560 × 1080 is 64:27, about 1.6% wider.
- Shape, not size: two pictures with the same ratio can have very different pixel counts. 1280 × 720 and 3840 × 2160 are both 16:9.
- Decimal ratios work as well: a ratio of 2.39 to 1 is 239:100 in whole numbers, and the missing side is worked out the same way.
- Portrait or landscape: 9:16 is 16:9 standing up, and upright sizes are compared with upright ratios.
- Private: nothing you type is sent or saved.