Aspect ratio calculator
Enter a width and height to get the simplified ratio, or pick a ratio like 16:9 and one side to get the other. Common sizes for the ratio are listed below.
Worked example
Simplify a monitor size, then size a video for the same ratio.
Width 2560, height 1440 Ratio 16:9, width 1280
2560 × 1440 → 16:9 (1.7778) 16:9 at 1280 wide → 1280 × 720
Common mistakes
Rounding the ratio, not the size
Work out the missing side from the full ratio and round only the result, or small errors add up.
Odd pixel counts for video
Many video encoders need even widths and heights. If the result is odd, step to the nearest even size.
Mixing up width and height
9:16 is portrait and 16:9 is landscape. The first number is always the width.
Stretching instead of cropping
Changing an image’s ratio means cropping or adding bars. Resizing to a new ratio without either distorts it.
How it works
- 1
Enter a size
Type the width and height in pixels (or any unit). The ratio is reduced to whole numbers, with its decimal value.
- 2
Find a missing side
Pick a preset or type a ratio such as 1.85:1, then enter a width or a height to get the other.
- 3
Check common sizes
The table lists familiar screen and media sizes at that ratio, and marks those that are only close to it.
Questions
- How do I calculate an aspect ratio?
- Divide the width and height by their greatest common divisor. For 1920 × 1080 that is 120, which gives 16:9.
- Is 21:9 really 21:9?
- Not exactly. “21:9” monitors are usually 2560 × 1080 (64:27) or 3440 × 1440 (43:18), both a little wider than 21:9. The table marks such sizes as close rather than exact.
- Why is 1366 × 768 not exactly 16:9?
- It reduces to 683:384, about 1.779. It is sold as 16:9 (1.778) because it is within a fraction of a pixel of it.
- What ratio should I use for social video?
- 9:16 (such as 1080 × 1920) fills a phone screen held upright; 1:1 and 4:5 (1080 × 1350) suit feeds; 16:9 suits landscape players.