You enter a width and height in pixels. The tool computes their greatest common divisor (GCD) using the Euclidean algorithm and divides both dimensions by it to produce the simplest whole-number ratio. The resize section applies the original width-to-height proportion to compute a matching dimension.
The GCD of 1920 and 1080 is 120. Dividing both by 120 gives 16 and 9, so the aspect ratio is 16:9. This is the standard widescreen format used by most monitors and TVs.
Instagram feed posts typically use 1:1 (square) or 4:5 (portrait). Stories and Reels use 9:16 (vertical). YouTube thumbnails and videos use 16:9. Twitter/X images perform well at 16:9 or 2:1.
Yes, the ratio is purely mathematical — it works with any unit as long as both dimensions use the same unit. The "px" label is just a default hint for digital use.
Non-standard dimensions may not reduce to a familiar ratio. This happens with cropped or resized images. The result is still mathematically correct; it just does not match a common preset.
Estimate only. Results reflect your inputs and standard formulas. Double-check important decisions independently.