πΌοΈ Aspect Ratio Calculator
Solve for width, height, or ratio. Perfect for video, images, and screens.
Aspect ratio
Common Resolutions at 16:9
| Label | Width | Height | Megapixels |
|---|---|---|---|
| HD 720p | 1280 | 720 | 0.9 |
| Full HD 1080p | 1920 | 1080 | 2.1 |
| QHD 1440p | 2560 | 1440 | 3.7 |
| 4K UHD | 3840 | 2160 | 8.3 |
| 8K UHD | 7680 | 4320 | 33.2 |
How to Use This Aspect Ratio Calculator
Aspect ratio is the proportional relationship between width and height, written as W:H. This tool solves whichever value you leave unknown. Pick a preset like 16:9, enter the dimension you know, and choose what to solve for. Video editors use it to resize footage without distortion, designers use it for responsive layouts, and photographers use it to plan crops.
Click a preset (16:9, 4:3, 1:1, 9:16, 21:9, 3:2) or type your own width and height.
Choose what to solve for: the ratio itself, the height from a known width, or the width from a known height.
If solving for a dimension, enter the target ratio in the Ratio W and Ratio H fields, then read the result.
What Is Aspect Ratio?
Aspect ratio describes shape, not size. A 16:9 phone screen and a 16:9 cinema display have the same proportions at wildly different sizes. The ratio is found by dividing width by height and reducing to simplest terms: 1920 Γ· 1080 = 1.778, and 16 Γ· 9 = 1.778, so 1920Γ1080 is 16:9. Keeping the ratio constant while scaling is what prevents the stretched or squished look.
The dominant ratios today: 16:9 for HDTV, YouTube, and most monitors; 9:16 for TikTok, Reels, and Shorts (the same ratio flipped vertical); 1:1 for Instagram posts; 4:3 for older TV and some tablets; 3:2 for DSLR photos; 21:9 for ultrawide monitors and cinematic video.
The Math Behind It
To simplify 1920:1080, find the greatest common divisor (120) and divide: 1920/120 = 16, 1080/120 = 9. To find the height of a 16:9 video that is 1280 wide: height = 1280 Γ· (16/9) = 1280 Γ 9/16 = 720. This cross-multiplication is all the calculator does, instantly and without rounding errors.
Worked Example
You shot vertical video for TikTok (9:16) and want a 1080-wide export. Set mode to solve for height, ratio 9:16, width 1080. Height = 1080 Γ 16/9 = 1920. Your export is 1080Γ1920, the standard full-HD vertical frame. Another case: a 4000Γ3000 photo. 4000 Γ· 3000 = 1.333 = 4/3, so it is a 4:3 image that will crop cleanly to any 4:3 frame.
Common Mistakes to Avoid
The biggest mistake is resizing by changing only one dimension, which distorts the image. Always scale both dimensions by the same factor, or crop. Another is confusing 16:9 with 16:10 (older monitors): a 1920Γ1200 display is 16:10, and 16:9 content will letterbox on it. When in doubt, compute the ratio first with this tool before exporting.
Frequently Asked Questions
What is the aspect ratio of 1920x1080?
16:9. Divide 1920 by 1080 to get 1.778, which equals 16/9. This is the standard Full HD ratio used by HDTVs, YouTube, and most monitors.
How do I calculate aspect ratio from width and height?
Divide width by height, then express as a ratio in lowest terms. For 1920Γ1080: 1920/1080 = 1.778 = 16:9. This calculator does the GCD simplification for you automatically.
What aspect ratio is best for YouTube?
16:9 is the standard for YouTube (1920Γ1080 or 3840Γ2160). For YouTube Shorts, use 9:16 vertical (1080Γ1920). Uploading the wrong ratio causes black bars or cropping.
What is the difference between 16:9 and 4:3?
16:9 is widescreen (1.78:1), the modern HDTV standard. 4:3 (1.33:1) is the older nearly-square TV format. 16:9 shows about 33 percent more horizontal content than 4:3 at the same height.
How do I resize an image without distortion?
Keep the aspect ratio locked: scale width and height by the same factor, or crop to the target ratio first. This calculator tells you the exact missing dimension so nothing stretches.