Aspect ratio calculator
Give the original width and height, then one new dimension. The other is worked out so the picture keeps its shape. The ratio is reduced to lowest terms and matched to its common name where one exists.
- Aspect ratio
- 16:9
- Common name
- 16:9
- As a decimal
- 1.7778
- Original megapixels
- 2.07
- Orientation
- Landscape
- Height ÷ width
- 0.5625
The formula
Ratio = width ÷ height, reduced by the greatest common divisor. New height = new width ÷ ratio; new width = new height × ratio. If both new dimensions are given, the width is used.
Worked example
1920 × 1080 reduces to 16:9. Scaled to a width of 1280, the height must be 720 to avoid stretching.
How to use it
- 1Fill in only one of the two new dimensions and leave the other at zero.
- 2Units do not matter — pixels, centimetres or inches — as long as the originals share one.
- 3Expect a decimal result when the new size does not divide evenly. Round to the nearest whole pixel.
Questions people ask
Why does 1366 × 768 not show as 16:9?
Because it is not quite: it reduces to 683:384, about 1.779 against 16:9’s 1.778. It is close enough that the common name is still matched, and the exact reduced ratio is shown as well.
What ratio should I use for video?
16:9 for most screens and online video, 9:16 for vertical phone video, 1:1 or 4:5 for social media feeds, and 2.39:1 for a cinema look.
Last reviewed: 2026-10-20