Aspect ratio calculator
Work out the missing dimension so nothing gets stretched.
- Runs in your browser — nothing you enter is uploaded
- No sign-up, no quotas, free to use as often as you like
How it works
Every time something is resized, one dimension is known and the other has to follow. Guessing produces stretched images and letterboxed video, and the arithmetic is simple enough that a calculator is faster than opening a design tool.
Enter the original, then one new dimension
Give the original width and height, then whichever new dimension you know. The other is calculated so the proportions stay identical. Leave a field at zero to ignore it.
The ratio in lowest terms
The original dimensions are reduced by their greatest common divisor, so 1920 × 1080 is reported as 16:9 rather than 1920:1080. Common ratios are named where they match.
Ratios worth knowing
16:9 is widescreen video. 9:16 is vertical video for phones. 1:1 is square. 4:5 is the tall feed post. 4:3 is older standard video and many camera sensors. 3:2 is the classic photographic frame. 21:9 is ultrawide.
Rounding
Results are rounded to whole pixels, since fractional pixels do not exist. On extreme ratios that rounding can shift the proportions by a fraction of a percent, which is invisible.
Aspect ratio calculator — questions
How do I resize without distorting?
Keep the ratio: set one dimension and let this calculate the other.
What ratio is 1920 by 1080?
16:9, the standard widescreen ratio.
Why is my result off by a pixel?
Dimensions are rounded to whole pixels. The difference is not visible.