Last updated 23 August 2026
The formula
New height = new width × (original height ÷ original width). Holding that ratio constant is what keeps a resized image or video from looking stretched or squashed.
Scaling is not cropping
Scaling keeps everything in the frame and changes its size. Cropping keeps the size and throws part of the frame away. This calculator does the first one: it tells you the width and height that preserve the original shape, so nothing stretches.
That distinction matters when a platform demands a ratio your footage does not have. A 16:9 video pushed into a 9:16 slot has to lose about two-thirds of its width, and no amount of scaling avoids that — you either crop, or you accept bars down the sides. Working the numbers out first tells you which of those you are signing up for.
Rounding is the other thing to watch. Exact ratios rarely land on whole pixels, so a value may come back a pixel off what you expected. For video, even numbers are safer: some encoders reject odd dimensions outright.
Related guide: Social media image sizes, and why they keep changing
Common questions
How is the missing dimension calculated?
New height = new width × (original height ÷ original width). That ratio between the original dimensions is held constant, so the image or video resizes without stretching or squashing.
What do the preset buttons do?
They fill in common standard ratios — 16:9 for widescreen video, 9:16 for vertical/story format, 1:1 for square, 4:3 for older video or print — so you don't need to know the exact pixel values.
Why does the simplified ratio matter?
It's a quick way to recognize a standard format. 1920×1080 and 1280×720 look like different numbers, but both simplify to 16:9 — the same shape at different sizes.