Ratio Size Calculator
Enter a ratio such as 16:9 or 3:2 and one known side, the width or the height. The calculator finds the other side, simplifies the ratio and shows the area and diagonal.
- Any ratio
- Width or height
- Simplest form
Use any unit for the known side. Decimal ratios like 2.39:1 work too.
A ratio keeps shapes the same as they get bigger or smaller. Video, photos, screens and paper all use fixed ratios. Knowing one side and the ratio is enough to find the other, so images can be resized without stretching or cropping.
Common ratio chart
Width to height. Search for a ratio.
| Ratio | Decimal | Height at 1920 wide | Used for |
|---|---|---|---|
| 1:1 | 1 | 1920 | Social posts |
| 4:3 | 1.333 | 1440 | Old TV, tablets |
| 3:2 | 1.5 | 1280 | Photos, 35 mm |
| 16:10 | 1.6 | 1200 | Laptops |
| 16:9 | 1.778 | 1080 | HD video |
| 21:9 | 2.333 | 823 | Ultrawide |
| 2.39:1 | 2.39 | 803 | Cinema |
| 9:16 | 0.5625 | 3413 | Phone video |
Heights shown for a width of 1,920. Use the calculator for any other size.
Width and height
16:9 and others. Slide the width.
The square in the drawing marks a 1:1 area, so you can see how much wider the frame is.
How to scale by a ratio
Cross-multiply. Step through it.
Write the ratio
a : b.
To simplify a ratio, divide both parts by their greatest common divisor. 1920:1080 becomes 16:9.
Scale, crop or stretch
Fitting one ratio into another. Compare them.
Keep the ratio, change the size.
Cut to a new ratio.
Force a new ratio.
Letterboxing adds bars to fit a wide picture on a narrower screen without losing anything.
Before resizing
Avoid distortion. Tick each item.
Tick each item as you go.
Lock the aspect ratio in your editor before changing one side. The other then follows automatically.
What you get
Scaled size. Each tile explains one result.
Width or height.
Reduced form.
x : 1.
Width × height.
Corner to corner.
The diagonal is handy for screens, which are sold by diagonal size.
Frequently Asked Questions
No question matches that search.
How do I resize keeping the ratio?
New height = new width × ratio height ÷ ratio width.
What is 16:9 at 1280 wide?
720 high.
What is 4:3 at 1024 wide?
768 high.
How do I find the ratio of 1920 × 1080?
Divide both by 120: 16:9.
What is 3:2 at 6000 wide?
4000 high.
What ratio is A4 paper?
1 : 1.414, the square root of 2.
What is 21:9 at 3440 wide?
About 1474, sold as 1440 because 3440 × 1440 is really 43:18.
Resize without stretching
Enter the ratio and one side to get the other. Images, video and layouts keep their shape, whatever size you need.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.