Aspect Ratio Calculator
Find the aspect ratio of any width and height, resize an image or video without distortion, or get a size from a ratio like 16:9.
Example loaded: 1920 × 1080. Change the numbers and select Calculate.
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Quick answer
The aspect ratio is the width divided by the height, written as two simple numbers. A 1920 × 1080 screen is 16:9, because both numbers divide by 120. To resize without stretching, multiply the new width by the original height and divide by the original width.
Choose Find ratio to get the ratio of a size, Resize to scale an image or video, or From a ratio to get a size such as 16:9 at a width of 1920.
How to calculate an aspect ratio
Find the ratio from width and height
- Write the width and height, for example 1920 and 1080.
- Find their greatest common divisor. For 1920 and 1080 it is 120.
- Divide both by it: 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9. The ratio is 16:9.
Resize without distortion
- Pick the new width, for example 1280.
- New height = 1280 × 1080 ÷ 1920 = 720.
- The new size is 1280 × 720, still 16:9.
Find a size from a ratio
For a 4:3 ratio at a width of 1000, the height is 1000 × 3 ÷ 4 = 750. For a height, the width is height × 4 ÷ 3.
If you need the other way, such as simplifying any pair of numbers, try the ratio calculator.
Common aspect ratios
| Ratio | Width ÷ height | Typical use |
|---|---|---|
| 1:1 | 1 | Square posts, profile photos, album art |
| 5:4 | 1.25 | Some monitors, 8×10 prints |
| 4:3 | 1.333 | Older TVs, iPad, many compact cameras |
| 3:2 | 1.5 | DSLR and mirrorless photos, 35mm film |
| 16:10 | 1.6 | Many laptops and monitors |
| 16:9 | 1.778 | HD and 4K video, YouTube, most TVs and monitors |
| 2:1 | 2 | Some phone screens, wide banners |
| 21:9 | 2.333 | Ultrawide monitors, cinematic video |
| 4:5 | 0.8 | Portrait feed photos on social media |
| 3:4 | 0.75 | Portrait photos |
| 2:3 | 0.667 | Portrait photos and posters |
| 9:16 | 0.563 | Vertical video, Stories, Reels, Shorts, TikTok |
Platforms change their recommended sizes from time to time, so check the current guidance of the site you upload to.
Common resolutions and their ratios
| Resolution | Name | Aspect ratio | Decimal |
|---|---|---|---|
| 1920 × 1080 | Full HD | 16:9 | 1.778 |
| 1280 × 720 | HD | 16:9 | 1.778 |
| 3840 × 2160 | 4K UHD | 16:9 | 1.778 |
| 2560 × 1440 | QHD, 1440p | 16:9 | 1.778 |
| 1366 × 768 | Common laptop | 683:384 | 1.779 |
| 1024 × 768 | XGA | 4:3 | 1.333 |
| 1080 × 1080 | Square post | 1:1 | 1 |
| 1080 × 1350 | Portrait post | 4:5 | 0.8 |
| 1080 × 1920 | Vertical video | 9:16 | 0.563 |
| 2560 × 1080 | Ultrawide | 64:27 | 2.37 |
| 3440 × 1440 | Ultrawide QHD | 43:18 | 2.389 |
| 4096 × 2160 | DCI 4K | 256:135 | 1.896 |
Some resolutions, such as 3440 × 1440, do not divide into small numbers. They are sold under the nearest common name, here 21:9.
Worked examples
- 1920 × 1080: divide by 120 to get 16:9.
- 1080 × 1350: divide by 270 to get 4:5, the portrait feed size.
- Shrink a photo: a 4000 × 3000 photo resized to a width of 800 has a height of 800 × 3000 ÷ 4000 = 600.
- From a ratio: 9:16 at a height of 1920 has a width of 1920 × 9 ÷ 16 = 1080.
- Fit a video: a 16:9 video at a width of 1000 is 1000 × 562.5, so round to 1000 × 562 or 1000 × 563.
Select Load example above to try one in the calculator.
Frequently asked questions
What is an aspect ratio?
It is the proportional relationship between the width and the height of an image, video or screen, written as two numbers such as 16:9. It does not say how big the picture is, only its shape.
How do I calculate an aspect ratio?
Divide the width and the height by their greatest common divisor. For 1920 × 1080 the divisor is 120, so the ratio is 16:9.
How do I find the height from a width and an aspect ratio?
Multiply the width by the ratio height and divide by the ratio width. For 16:9 at a width of 1920, the height is 1920 × 9 ÷ 16 = 1080.
How do I resize an image without stretching it?
Keep the same aspect ratio. Choose a new width or a new height and let the calculator work out the other side, then use that size.
What does 16:9 mean?
It means the width is 16 units for every 9 units of height. It is the standard shape for HD and 4K video, most TVs and many monitors.
What is the difference between aspect ratio and resolution?
Resolution is the number of pixels, such as 1920 × 1080. Aspect ratio is only the shape, such as 16:9. Many different resolutions share the same ratio.
What aspect ratio should I use for social media or video?
Common choices are 16:9 for landscape video, 9:16 for vertical video, 1:1 for square posts and 4:5 for portrait feed photos. Platforms update their rules, so check their current guidance.
Why does my ratio come out as large numbers?
Some sizes, such as 3440 × 1440 (43:18), do not simplify to small numbers. The calculator shows the nearest common ratio, which is 21:9 for that size.
Can I use decimals?
Yes. You can enter widths and heights with decimals, for example from inches or centimetres, and the ratio is worked out in the same way.
Is my data stored?
No. Everything is calculated in your browser and nothing is sent anywhere.
About this calculator
Written by Umar Khan. The calculator finds the greatest common divisor of the width and height to get the simplest ratio, and resizes with simple proportions. Your numbers stay in your browser. Last updated November 10, 2026. Questions or corrections: [email protected].
Written by Umar Khan
Umar Khan is a PhD student in engineering at NTNU, the Norwegian University of Science and Technology, in Norway. Every formula and worked example on this page is shown in full so you can check each result yourself. Corrections are welcome at [email protected].
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For information only, not professional advice.
Written by Umar Khan. Last updated: November 10, 2026.