How is the aspect ratio reduced?

The width and height are divided by their greatest common divisor, so 1920×1080 reduces to 16:9 and 1280×1024 reduces to 5:4.

How do I keep the aspect ratio when resizing?

New height = new width ÷ (original width ÷ original height). Enter a target width and the tool computes the height for you so the image is not stretched.

Is anything uploaded?

No — every calculation runs locally in your browser and nothing is sent to a server.

Aspect Ratio Calculator

Find a ratio and scale dimensions while keeping it locked.

Aspect ratio calculator

Reduce any width × height to a clean aspect ratio in lowest terms — like 16:9, 4:3 or 21:9 — then resize to a new width and get the exact height that keeps the ratio locked.

Useful for video frames, photos, thumbnails and responsive layouts where stretching or letterboxing matters. Everything runs in your browser.