Aspect Ratio Calculator
Find the ratio from width and height, or calculate missing dimensions. Visual preview. Useful for video, print, and social media.
Common aspect ratios
Frequently asked questions
What is an aspect ratio?
An aspect ratio is the proportional relationship between width and height, expressed as W:H. For example, 16:9 means for every 16 units of width there are 9 units of height. It stays the same regardless of the actual pixel dimensions.
How is the simplified ratio calculated?
The tool finds the greatest common divisor (GCD) of width and height using the Euclidean algorithm, then divides both by it. For example, 1920÷240=8 and 1080÷240=4.5 — wait, GCD(1920,1080)=120, giving 16:9.
Why does 1920×1080 give 16:9 but 1280×720 also gives 16:9?
Because they are the same ratio. 1280÷720 = 1920÷1080 = 1.7778... = 16/9. Any resolution with that proportional relationship will give the same simplified ratio.
What aspect ratio should I use for YouTube thumbnails?
YouTube recommends 16:9 at 1280×720 pixels minimum, with 1920×1080 ideal. The thumbnail is displayed at various sizes so the ratio must be 16:9 or it will be letterboxed or cropped.
What is the difference between 4:3 and 16:9?
4:3 (1.33:1) is closer to square — it was the standard for CRT TVs and early computer monitors. 16:9 (1.78:1) is wider and became the standard for HD video. Content made in 4:3 gets pillarboxed (black bars on sides) on 16:9 screens.