Image Size Calculator
Calculate a proportional image, video or screen dimension without uploading a file. Enter the original pixel width and height, then supply either a target width or target height to solve the missing side while preserving the original shape.
The result simplifies the original aspect ratio with the greatest common divisor, rounds the calculated side to the nearest whole pixel, compares the target width with the original as a scale percentage and reports the approximate target megapixels.
How to use this calculator
- Enter the original width and height in pixels.
- Choose whether to calculate target height or target width and enter the known side.
- Review the proportional size, aspect ratio, scale and megapixels.
Frequently asked questions
Does this resize an image file?
No. It calculates dimensions only and does not read, upload or modify a file.
How is the missing dimension calculated?
Target height equals target width times original height divided by original width; the inverse formula solves width.
Why can the ratio be different from 16:9?
The calculator simplifies the exact dimensions. Images that were cropped or rounded may not reduce to a familiar standard ratio.