How is the ratio simplified?

Using the greatest common divisor (GCD) of the width and height — the same math behind simplifying any fraction. A 1920×1080 frame has a GCD of 120, so it reduces to 16:9. This gives you the exact lowest-terms ratio, not an approximation.

Why does it show a "closest common ratio" that isn't exact?

Real-world footage, sensor crops, and exported images rarely land on a perfectly clean ratio — a photo might be 1920×1077 instead of a clean 16:9. The closest-match feature compares your decimal ratio against the common presets (16:9, 4:3, 1:1, 21:9, 9:16, 3:2, 5:4) and tells you which one it's nearest to, and by how much, so you know whether a small crop would get you to a standard ratio.

How does solving for a missing dimension work?

Given a ratio (say 16:9) and one known dimension (say a width of 1920), the other dimension is computed by cross-multiplying: height = width × (ratio height ÷ ratio width). This is the calculation you'd do by hand to figure out, for example, what height to export a 2560px-wide image at to keep it 21:9 for an ultrawide banner.

Is this useful for anything beyond video?

Yes — the same math applies to photo crops, print sizes, social media image specs, UI frame sizing, and any layout where you need to keep proportions consistent while scaling. Video editors use it for framing and export presets, photographers for crop ratios, and designers for responsive image containers.

ASPECT RATIO CALCULATOR

Simplify dimensions to a ratio, or solve for a missing width or height from a known ratio. Built for video, photo, and design work.

Common presets

Width (px)

Height (px)

16:9

Simplified ratio	16:9
Decimal ratio	1.7778
Closest common ratio	16:9 (exact match)

How to use the aspect ratio calculator

1
Pick a mode: simplify a width/height pair to its ratio, or solve for a missing dimension from a known ratio.
2
Type your numbers, or click a common preset (16:9, 4:3, 1:1, 21:9, 9:16, 3:2) to fill the fields instantly.
3
Read the simplified ratio and closest common match, or the computed missing dimension.

Questions

How is the ratio simplified?: Using the greatest common divisor (GCD) of the width and height — the same math behind simplifying any fraction. A 1920×1080 frame has a GCD of 120, so it reduces to 16:9. This gives you the exact lowest-terms ratio, not an approximation.
Why does it show a "closest common ratio" that isn't exact?: Real-world footage, sensor crops, and exported images rarely land on a perfectly clean ratio — a photo might be 1920×1077 instead of a clean 16:9. The closest-match feature compares your decimal ratio against the common presets (16:9, 4:3, 1:1, 21:9, 9:16, 3:2, 5:4) and tells you which one it's nearest to, and by how much, so you know whether a small crop would get you to a standard ratio.
How does solving for a missing dimension work?: Given a ratio (say 16:9) and one known dimension (say a width of 1920), the other dimension is computed by cross-multiplying: height = width × (ratio height ÷ ratio width). This is the calculation you'd do by hand to figure out, for example, what height to export a 2560px-wide image at to keep it 21:9 for an ultrawide banner.
Is this useful for anything beyond video?: Yes — the same math applies to photo crops, print sizes, social media image specs, UI frame sizing, and any layout where you need to keep proportions consistent while scaling. Video editors use it for framing and export presets, photographers for crop ratios, and designers for responsive image containers.