Aspect Ratio Calculator
Enter the original width and height, then the new width or the new height you want. You get the simplified ratio and the matching other side, to keep the shape.
Your numbers
How we calculate it
The aspect ratio is width : height reduced to the smallest whole numbers by dividing both by their greatest common divisor. For 1920 × 1080 the divisor is 120, which gives 16:9.
To resize while keeping the shape, the new height is new width × original height ÷ original width, and the new width is new height × original width ÷ original height. So a 1920 × 1080 picture made 1280 wide is 1280 × 1080 ÷ 1920 = 720 high. The whole pixel size is the result rounded to the nearest pixel, and never less than 1.
Assumptions and limits
- If you type decimals the ratio is shown as a decimal such as 1.7782:1 instead of whole numbers.
- Many real sizes are not exactly 16:9. For example 1366 × 768 reduces to 683:384, which is very close to 16:9. A common name is shown only when the ratio matches exactly.
- Rounding to whole pixels changes the ratio a little. Check the result is acceptable for your use.
Frequently asked questions
What is the aspect ratio of 1920 × 1080?
1920 × 1080 is 16:9, the usual shape for HD video and most monitors. 3840 × 2160 (4K) and 1280 × 720 are also 16:9.
How do I resize an image without stretching it?
Keep the aspect ratio. Choose whether you know the new width or the new height, enter it, and use the other number that the calculator gives, rounded to a whole pixel.
What is 21:9?
21:9 is the shape of ultrawide monitors and cinema-style video. Real ultrawide screens such as 3440 × 1440 are close to 21:9 but reduce to other exact ratios, here 43:18.
Related calculators
- PX to REM ConverterEnter a size, choose the direction and the base font size.
- Hex to RGB Color ConverterType a color as hex, rgb() or hsl().
- Percent of a Number CalculatorEnter a percentage and a number to find the amount, plus the totals when you add or subtract that percentage.
- Length ConverterEnter a length, choose the unit it is in and the unit you want.
Worked example (a fixed example using the starting numbers, it does not change as you type)
Inputs: Original width = 1920; Original height = 1080; I know the new = Width (find the height); New size = 1280.
- Aspect ratio 16:9
- Decimal ratio 1.7778
- Common name 16:9 widescreen (HD and 4K video, most monitors)
- New height 720
- Whole pixels 720
Embed this calculator
Add this calculator to your own page. Paste the code where you want it. The small link keeps credit to the source.