loot.toolsGive it a ratio and one dimension, and it works out the other. Set 16:9 and a width of 1920 and it tells you the height is 1080. Change the height and the width updates to match. It keeps your proportions exact so images and video don't stretch or squash when you scale them.
An aspect ratio is the relationship between width and height, written as two numbers like 16:9. To keep the same shape at a different size, both numbers have to scale by the same factor. The calculator does that math for you and also reduces the ratio to its simplest form using the greatest common divisor, so 1920 by 1080 shows up as 16:9.
Video editors matching footage to 16:9 or 21:9 timelines. Designers sizing banners and thumbnails. Photographers cropping to 3:2 or 4:3. Anyone posting to social media who needs a 1:1 square or a 9:16 vertical. Pick a preset or type your own numbers and the dimensions stay locked to the ratio.