Aspect Ratio Calculator
Aspect ratio calculator works out Aspect ratio and Ratio width term from What do you want, Width and Height. The default figures on this page give aspect ratio of 16:9; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
2 steps
- Ratio = 1920 : 1080
- Divide both by gcd(1920, 1080) = 120 → 16:9
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
3 sources
What the aspect ratio calculator calculates
Reduces a width and height to its simplest aspect ratio, resizes a resolution while preserving that ratio, derives physical screen width and height from a diagonal, fits content into a bounding box, and reports pixel density.
How to use this aspect ratio calculator
Enter What do you want, Width, Height and New width. Aspect ratio updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Aspect ratio, Ratio width term and Ratio height term.
The method follows Wikipedia, "Aspect ratio (image)" — standard named ratios and their conventional labels, Euclid, Elements, Book I, Proposition 47 — the Pythagorean relation d² = w² + h² used for diagonals and Euclid, Elements, Book VII, Propositions 1–2 — the Euclidean algorithm used to reduce the ratio.
1920 × 1080 simplifies to 16:9 example
With What do you want: ratio, Width: 1920, Height: 1080, the calculator returns Aspect ratio: 16:9, Ratio width term: 16, Ratio height term: 9. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Aspect ratio, Ratio width term and Ratio height term. The inputs you can vary are What do you want, Width, Height, New width, New height and Ratio width.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How do I find my aspect ratio?
Reduces a width and height to its simplest aspect ratio, resizes a resolution while preserving that ratio, derives physical screen width and height from a diagonal, fits content into a bounding box. Open “How this is worked out” beside the result to see each step for your own figures.
How do I calculate aspect ratio?
It needs What do you want, Width, Height, New width, New height and Ratio width. Nothing else is required, and the figures stay in your browser.
Is 1280x720 a 16:9 aspect ratio?
Reduces a width and height to its simplest aspect ratio, resizes a resolution while preserving that ratio, derives physical screen width and height from a diagonal, fits content into a bounding box. On the figures this page opens with — width 1,920 and height 1,080 — the aspect ratio is 16:9. Put your own figures in their place and the working updates beside the result.
How do I resize an image to aspect ratio?
The result gives Aspect ratio, Ratio width term, Ratio height term, Width ÷ height, Ratio as x:1 and Inverse (portrait) ratio, each labelled with its unit so the figure can be read on its own.
What information do I need for the aspect ratio calculator?
You need What do you want, Width, Height, New width, New height, Ratio width, Ratio height and Diagonal. The page opens with default figures that give aspect ratio of 16:9, so you can see the scale before entering your own.
What does this aspect ratio calculator show?
It shows Aspect ratio, Ratio width term, Ratio height term, Width ÷ height, Ratio as x:1, Inverse (portrait) ratio, Width and Height, with the working and any warnings for your entries.