Aspect Ratio Calculator
Calculate 16:9, 4:3, 9:16, and custom aspect ratios and resize pixel dimensions without stretching.
Written by Anil Gautam · Updated
Why does my screen size show a ratio like 683:384?
The calculator reduces width and height to the smallest exact whole numbers, and many sizes sold under a familiar ratio are only close to it. A 1366 × 768 laptop screen reduces to 683:384, with a decimal of 1.779 against 1.778 for true 16:9. On a 1440 × 900 screen the result is 8:5, which is 16:10 in lowest terms.
Ultrawide monitors are the clearest case. The 21:9 preset loads 2560 × 1080, which reduces to 64:27 with a decimal of 2.370, and 3440 × 1440 reduces to 43:18, or 2.389, while an exact 21:9 is 2.333. To compare shapes, use the decimal, which is width divided by height to three places. A decimal below 1 means a portrait shape, so 1080 × 1920 reads 9:16 and 0.563. When your size matches a preset's ratio, that preset button gets a coloured outline, and the list of common resolutions appears only when the reduced ratio is exactly 16:9, 9:16, 4:3, 1:1 or 3:2.
How do I avoid odd or fractional sizes?
The side you type stays fixed, and the highlighted side is calculated and rounded to the nearest whole number. From 1920 × 1080, a new width of 1000 gives an exact height of 562.5, shown as 563, and 1000 × 563 has a decimal of 1.776, slightly off 16:9. For an exact 16:9 result, pick a width divisible by 16: 1024 gives 576 and 1280 gives 720. Many video encoders expect even numbers on both sides, so check the calculated box before exporting video.
The numbers do not have to be pixels. Centimetres, inches or any other unit work because only the proportion matters, so a 6 × 4 inch print reads 3:2.
How do I change a photo to a different ratio?
This calculator always keeps the shape you start with: a 4032 × 3024 phone photo, which is 4:3, resized to a width of 1200 becomes 1200 × 900. Turning that photo into a 4:5 portrait means cropping some of its width. Enter 4 and 5 as the original size, then type 3024 as the new height: the width comes out as 2419, so a 2419 × 3024 crop keeps the full height. After cropping, Bulk Image Resizer can scale the files with its aspect ratio lock turned on.