Aspect Ratio Calculator
Work out the ratio of any size, or resize without distorting it. Everything updates as you type, and the preview is drawn to true proportion.
Dimensions
Ratio
Presets:
Drawn to true proportion — not to real-world size.
What an aspect ratio actually is
An aspect ratio is the relationship between width and height, stripped of any particular size. 1920 x 1080, 1280 x 720 and 3840 x 2160 are all 16:9 — same shape, different amounts of detail. That is why a ratio is written as two numbers with no units: it describes proportion, not dimensions.
To find it, divide both numbers by their greatest common divisor. For 1920 x 1080 that divisor is 120, giving 16:9.
Common ratios and where they are used
| Ratio | Decimal | Typical resolutions | Where you meet it |
|---|---|---|---|
| 16:9 | 1.78 | 1920x1080, 2560x1440, 3840x2160 | Most monitors, TVs, YouTube |
| 16:10 | 1.60 | 1920x1200, 2560x1600 | Productivity monitors, MacBooks |
| 4:3 | 1.33 | 1024x768, 2048x1536 | Older monitors, iPad, slides |
| 21:9 | 2.33 | 2560x1080, 3440x1440 | Ultra-wide monitors, cinema |
| 32:9 | 3.56 | 3840x1080, 5120x1440 | Super ultra-wide |
| 3:2 | 1.50 | 2256x1504, 3000x2000 | Surface devices, 35mm photos |
| 1:1 | 1.00 | 1080x1080 | Square social posts |
| 9:16 | 0.56 | 1080x1920 | Reels, Shorts, TikTok |
Resizing without distortion
The single rule: change one dimension and let the other follow from the ratio. Multiply the width by the ratio height and divide by the ratio width to get the correct height. Scaling both freely is what produces stretched faces and squashed logos.
Tick Lock ratio above and the calculator enforces this — type a new width and the height is worked out for you.
Why a wider screen at the same diagonal is shorter
Diagonal size is quoted independently of shape, so two screens with the same diagonal but different ratios are different sizes. A 34-inch 21:9 monitor is noticeably shorter than a 34-inch 16:9 one would be, because the same diagonal is being spread further sideways. The screen size comparison draws that difference to scale, and the monitor size calculator gives you the actual width and height in inches.
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Frequently asked questions
How do I calculate an aspect ratio?
Divide the width by the height and simplify. For 1920 by 1080 the greatest common divisor is 120, which reduces to 16:9. This page does it as you type, and snaps to the recognised name when the result is one of the standard ratios rather than showing you something like 683:384.
How do I resize an image without distorting it?
Keep the ratio locked and change one side; the other follows automatically. Tick "Lock ratio", set the ratio you want, then type a new width and the height is calculated for you. Any other approach stretches the image.
What aspect ratio is my screen?
Press "Use my screen" and it fills in your actual resolution and works out the ratio. Most monitors and laptops are 16:9; many productivity monitors and MacBooks are 16:10; ultra-wides are 21:9 or 32:9.
What is the difference between 16:9 and 16:10?
16:10 is taller. At the same width, a 16:10 screen gives you about 11% more vertical space, which is why it is popular for writing and coding. 16:9 matches video content exactly, so films and most online video fill it without black bars.
Why does 1366 x 768 not simplify to 16:9?
Because it is not exactly 16:9 — it reduces to 683:384, which is very slightly wider. Manufacturers rounded to a convenient panel size. It is close enough that everyone calls it 16:9, and this calculator says so rather than showing the unhelpful exact fraction.
What ratio should I use for social video?
9:16 vertical for Reels, Shorts and TikTok; 1:1 square for feed posts that need to work everywhere; 16:9 for YouTube landscape. The preset buttons cover all three.