Aspect Ratio Calculator

Three questions about proportions, all in pixels. Give a size and one new dimension and the other one is worked out for you, with the unrounded figure shown next to the whole pixel so you can see which way it was rounded. Give a size on its own and you get the ratio in lowest terms, as a decimal, and the name it is sold under when it matches a standard such as 16:9, 4:3 or 21:9 ultrawide. The third mode fits a ratio inside a frame of another ratio and reports the letterbox or pillarbox bars in pixels. Fitted sizes are rounded down so the result never overflows the frame by a pixel.