How to calculate an aspect ratio
- Enter a width and height in pixels (or any unit) in Find the ratio. The simplified ratio, its decimal form and its common name appear, with a preview box of that shape.
- To resize while keeping the shape, enter a ratio (or tap a common one) and type the new width; the height is calculated. Type a height instead to get the width.
What aspect ratio means
An aspect ratio is the proportion between width and height, written as width:height. It is found by dividing both numbers by their greatest common divisor: 1920 and 1080 share 120, giving 16:9. The ratio says nothing about size: 1280×720, 1920×1080 and 3840×2160 (4K) are all 16:9. To scale while keeping the ratio, new height = new width × height ÷ width.
Common ratios: 16:9 for HD and 4K video, TVs and most monitors; 9:16 for vertical phone video; 4:3 for older TVs and iPads; 3:2 for most camera sensors; 1:1 for square posts; 4:5 for Instagram portrait posts; and 21:9 for ultrawide monitors. Some "21:9" monitors are really 64:27 (2560×1080) or 43:18 (3440×1440), which the calculator reports exactly.
When an image's ratio differs from its frame, it must be cropped, letterboxed (bars added) or stretched. Knowing the ratio first helps you crop video and photos correctly. The calculator works offline in your browser.
What is the aspect ratio of 1920×1080?
16:9. Divide both by 120.
How do I calculate the height for a 16:9 video 1280 pixels wide?
Height = 1280 × 9 ÷ 16 = 720 pixels.
Is 16:10 the same as 8:5?
Yes, mathematically. Screens are traditionally described as 16:10 so they are easy to compare with 16:9.