How to find an aspect ratio
Divide the width by the height to get a decimal ratio, then simplify. For whole numbers (like pixel dimensions), that means dividing both by their greatest common divisor — 1920 and 1080 share a greatest common divisor of 120, so 1920÷120 : 1080÷120 gives the familiar 16:9.
The unit you enter doesn't change the answer — a ratio is just a proportion, so 1920×1080 pixels and 19.2×10.8 inches simplify to the exact same 16:9.
When your measurement is "close to" a standard ratio, not exact
Real-world measurements (especially anything measured in inches or centimeters rather than counted in exact pixels) rarely land on a perfectly round ratio. This tool checks whether your result is close to a well-known standard (within a small tolerance) and shows that alongside the exact math — both the precise simplified ratio and the closest common name, since they can genuinely differ. A 3440×1440 ultrawide monitor, for example, is universally sold as "21:9," but its exact pixel ratio simplifies to 43:18, about 2.4% off from true 21:9.
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Frequently asked questions
How do I calculate an aspect ratio?
Enter the width and height above in any unit. For whole-number dimensions like pixels, you'll get the exact simplified ratio (like 16:9). For decimal measurements, you'll get the decimal ratio plus the closest standard name if one is close.
What is 1920x1080 as a ratio?
16:9 — the standard for most modern TVs, monitors, and video.
Does the unit (pixels, inches, cm, mm) change the ratio?
No — a ratio is a pure proportion between width and height, so it comes out the same regardless of which unit you measured in. The unit selector here is just a label for the "Original Dimensions" row.
Looking for screen dimensions from a diagonal size instead?
That's the reverse problem — see the Screen Size Calculator, which goes from a diagonal measurement and an aspect ratio to the actual width, height, and screen area.