Aspect ratio calculator
ImagesNo. 03 / 84
Find the missing width or height for any aspect ratio, with presets for 16:9, 4:3, 1:1 and more.
the number that stops a video from looking like a funhouse mirror.
work surface
Math, not advice — results are indicative.Read the disclaimer.
most-used utilities
A 16:9 thumbnail
Choose 16:9, set the width and read the height.
An Instagram square
Choose 1:1 and type the size you need.
A banner
Choose free, enter the width and height, and check the decimal ratio.
pro tips
Keep the ratio locked when resizing; changing both dimensions by eye is how faces get wider.
For print, work in pixels at 300 DPI: 6 by 4 inches is 1800 by 1200 pixels.
A 21:9 screen and a 16:9 screen are not the same shape, even if both are called widescreen.
what it does
An aspect ratio is the relationship between width and height, not a size. Pick 16:9, type a width and the height follows; type a height and the width follows. The preview box uses the real ratio, so it stretches exactly like the final image or video would.
It is the tool for resizing a video without letterboxing it, fitting an image into a card, checking whether two screens share a shape, or working out the height of a 21:9 banner at a given width.
A 1920 by 1080 image is 16:9. At 1280 wide it becomes 720 high. At 500 high it becomes about 889 wide. The simplified ratio is 16:9, and the decimal is about 1.7778, which is the number the maths actually uses.
Presets cover the common shapes; free mode reads the ratio from whatever width and height you type. The megapixel figure is there so you can see whether the result is a thumbnail or a poster.
quick answers
Is aspect ratio the same as resolution?
No. Aspect ratio is the shape; resolution is the number of pixels. A 1280 by 720 image and a 3840 by 2160 image are both 16:9.
Does changing the ratio distort the image?
Yes, if the pixels are stretched to the new shape. Crop or letterbox instead if you want to keep proportions.
Why is the simplified ratio useful?
It is the smallest whole-number version of the shape, which makes it easy to compare with standard formats like 16:9 or 4:3.