Aspect Ratio Calculator
Enter a width and height to get the simplified aspect ratio and decimal value, or lock a ratio like 16:9 and solve the missing dimension as you type — with a live preview of the shape.
Enter a width and height, or lock a ratio to solve a missing dimension.
An aspect ratio is the proportional relationship between an image's width and height, written as two numbers with a colon — 16:9, 4:3, 1:1. It ignores absolute size: 1280×720 and 3840×2160 are both exactly 16:9. Because it stays constant as content scales, it's the number to match whenever you resize, crop, or fit media into a container.
The calculator simplifies a width and height by dividing both by their greatest common divisor (GCD): for 1920×1080 the GCD is 120, so the ratio reduces to 16:9. The decimal form is width ÷ height — 1920 ÷ 1080 ≈ 1.78, meaning the image is 1.78 times as wide as it is tall. Lock a ratio and type one dimension, and it solves the other in reverse, rounded to the nearest pixel.
To resize without stretching, keep the ratio fixed: change one dimension and let the other recompute. When source and display ratios differ, content is fitted with bars instead of distorted — letterboxing adds horizontal bars above and below (a 2.39:1 film on a 16:9 screen), while pillarboxing adds vertical bars on the sides (4:3 footage on 16:9). To relate a ratio to a real screen's size or pixel density, see the What Is My Screen Size? and PPI Calculator tools.
Common aspect ratios
| Ratio | Decimal (W ÷ H) | Where you see it |
|---|---|---|
| 16:9 | 1.78 | Modern monitors, laptops, TVs, and most online video — 720p, 1080p, 1440p, and 4K are all 16:9 |
| 16:10 | 1.60 | MacBooks and many productivity laptops; a bit more vertical room than 16:9 |
| 21:9 | 2.33–2.37 | Ultrawide monitors and cinematic gaming; pixel dimensions usually reduce to 64:27 |
| 4:3 | 1.33 | Older TVs, early computer displays, many tablets and document scans |
| 3:2 | 1.50 | Surface devices, most photo camera sensors, and classic 35mm stills |
| 1:1 | 1.00 | Square format for profile pictures and some social feed images |
| 9:16 | 0.56 | Vertical video for phones — Stories, Reels, TikTok, and Shorts |
| 2.39:1 | 2.39 | Modern anamorphic widescreen cinema, the widest common theatrical format |