Aspect Ratio Calculator
Enter a width and a height and the aspect ratio calculator reduces them to lowest terms, or give it one new side and it finds the other at the same shape.
New height
- New height height = width x 9 / 16 = 1,280 x 9 / 16 = 720
- 720
- New size Exactly 16:9, in whole units.
- 1,280 x 720
- Aspect ratio Both sides divided by their greatest common divisor, 120: 1,920 / 120 = 16 and 1,080 / 120 = 9.
- 16:9
- As a decimal ratio Width divided by height, the way cinema formats such as 1.85:1 and 2.39:1 are written.
- 1.78:1
- Shape
- landscape (wider than tall)
- Common name HD and 4K television, most monitors and online video.
- 16:9
- Total pixels at the new size
- 921,600 (0.9216 megapixels)
- Scale factor The new width over the original. Both sides change by this same factor, which is what keeps the shape.
- 0.6667x
| Ratio | As a decimal | Used for | Common sizes |
|---|---|---|---|
| 1:1 | 1:1 | Square images and video | 1,080 x 1,080, 2,048 x 2,048 |
| 4:3 | 1.33:1 | Standard-definition TV, older monitors and most phone camera photos | 640 x 480, 1,024 x 768, 1,600 x 1,200, 4,032 x 3,024 |
| 3:2 | 1.5:1 | 35 mm film (a 36 x 24 mm frame) and most interchangeable-lens camera sensors | 3,000 x 2,000, 6,000 x 4,000 |
| 8:5 (usually written 16:10) | 1.6:1 | Many laptop and desktop displays | 1,280 x 800, 1,920 x 1,200, 2,560 x 1,600 |
| 16:9 | 1.78:1 | HD and 4K television, most monitors and online video | 1,280 x 720, 1,920 x 1,080, 2,560 x 1,440, 3,840 x 2,160 |
| 64:27 (sold as 21:9) | 2.37:1 | Ultrawide monitors sold as 21:9 | 2,560 x 1,080, 5,120 x 2,160 |
| 43:18 (sold as 21:9) | 2.39:1 | Ultrawide monitors sold as 21:9 | 3,440 x 1,440 |
| 37:20 | 1.85:1 | Flat widescreen cinema, 1.85:1 | 1,998 x 1,080, 3,996 x 2,160 |
| 9:16 | 0.56:1 | Vertical video on phones: 16:9 turned on its side | 720 x 1,280, 1,080 x 1,920 |
How the Aspect Ratio Calculator works
An aspect ratio is the shape of a rectangle written as width to height, W:H. It says nothing about size: a phone screen and a cinema screen can share a ratio and differ in width by a factor of more than a hundred.
Reducing a size to its ratio. Divide the width and the height by their greatest common divisor. 1920 x 1080 has a greatest common divisor of 120, and 1920 / 120 = 16 while 1080 / 120 = 9, so 1920 x 1080 is 16:9. This calculator does it in exact integer arithmetic, which matters for sizes that are close to a famous ratio without being on it. 1366 x 768, a common laptop panel, reduces to 683:384, not 16:9: it is 0.05% wider. Decimal ratios are scaled to whole numbers first, so 2.39:1 is 239:100.
Finding a missing side. Keeping the shape means scaling both sides by the same factor. For a new width, the height is the width times H / W; for a new height, the width is the height times W / H. Scaling 1920 x 1080 to a width of 1280 gives 1280 x 9 / 16 = 720, so the new size is 1280 x 720. When the answer is not a whole number of pixels it has to be rounded. A 16:9 image 1000 pixels wide would need a height of 562.5, and either 562 or 563 is off the ratio by less than a tenth of a percent. The sizes at exactly 16:9 are the multiples of 16 x 9, so the widths that work are multiples of 16: 992 x 558 and 1008 x 567 are the nearest.
The common ratios. 16:9 is the shape of HD and 4K television (1920 x 1080 and 3840 x 2160) and of most monitors and online video. 4:3 is the older television and computer shape, and still the shape of most phone camera sensors. 3:2 comes from the 36 x 24 mm frame of 35 mm film. 16:10, which reduces to 8:5, is common on laptops. 9:16 is 16:9 turned on its side, the shape of vertical phone video. 1:1 is a square.
"21:9" is a marketing name rather than a ratio. Ultrawide monitors sold under it are 2560 x 1080, which is exactly 64:27 (2.37:1), or 3440 x 1440, which is 43:18 (2.39:1). Neither reduces to 21:9, which would be 7:3 (2.33:1). Cinema formats are written as a decimal against 1 instead: 1.85:1 for flat widescreen and 2.39:1 for scope.
Aspect Ratio Calculator FAQ
How do I calculate an aspect ratio?
Divide the width and the height by their greatest common divisor. For 1920 x 1080 that divisor is 120, giving 16:9. For 1366 x 768 it is 2, giving 683:384, which is close to 16:9 but not equal to it.
How do I find the height for a new width?
Multiply the new width by H / W. At 16:9, a width of 1280 gives 1280 x 9 / 16 = 720. To find a width from a height, multiply by W / H instead.
What resolution is 16:9?
Any size whose width divided by height is 16/9: 1280 x 720, 1920 x 1080, 2560 x 1440 and 3840 x 2160 are the common ones. Every whole-pixel 16:9 size is a multiple of 16 x 9.
Is 21:9 really 21:9?
Usually not. 2560 x 1080 reduces to 64:27 and 3440 x 1440 to 43:18. True 21:9 would be 7:3, or 2.33:1. The name groups the ultrawide shapes, all of which are close to 2.4:1.
Why does my resized image have a fractional height?
Because most widths do not divide evenly at the ratio. A 16:9 image 1000 pixels wide would be 562.5 pixels tall. Rounding to 562 or 563 changes the shape by less than 0.1%, or you can pick a width that is a multiple of 16.