Free aspect ratio calculator. Enter any two of width, height, or ratio and the tool resolves the third. Includes common presets like 16:9, 21:9, 4:3, 32:9, and simplifies to lowest terms.
Type any two of width, height, or ratio. The tool solves for the third and also reports the simplified ratio.
Edit any two of width, height, or ratio. The tool locks the most recently edited field and solves for the unedited one. Ratio accepts forms like "16:9" or "1.7778".
Simplified
16:9
Decimal
1.7778
Orientation
-
Tip: enter width and height to read the ratio, or pick a preset and type one dimension to get the other. Aspect ratios like 16:9 always render identically regardless of scale — the browser just computes the other side.
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Aspect Ratio Calculator is a free, browser-based screen testing tool that lets you type any two of width, height, or ratio.
Cost: Free, no signup
Install: None — runs in the browser
Privacy: Runs locally, no uploads
Platforms: Windows, macOS, Linux, Android, iOS
Time: Under a minute
What Is Aspect Ratio?
Aspect ratio is the relationship between a rectangle's width and height, expressed as two whole numbers (like 16:9) or a decimal (like 1.7778). It determines whether content feels wide and cinematic, tall like a phone screen, or classic like a 4:3 TV. Two resolutions with the same aspect ratio — say 1920×1080 and 3840×2160 — will display the same image content just at different pixel densities. This calculator handles the three directions: given any two of (width, height, ratio), it solves for the third and auto-simplifies to lowest integer terms.
The Math
Aspect ratio is literally width / height. To simplify 1920×1080 to 16:9, divide both by their greatest common divisor (120): 1920/120 = 16, 1080/120 = 9. To find the width given ratio 16:9 and height 720, multiply: 720 × (16/9) = 1280. The calculator runs both flows live — type whichever two fields you know and it locks them in, solving for the third.
Common Aspect Ratios By Use Case
16:9 — modern HDTVs, all 1080p / 1440p / 4K gaming monitors, most YouTube.
16:10 — MacBooks and productivity-focused laptops (extra vertical space).
When you resize an image or video frame, you preserve visual fidelity by keeping the aspect ratio constant. Need a 4K (3840×2160) asset scaled to fit a 720-pixel-tall column? Use the calculator: 720 × (3840/2160) = 1280 wide. Changing just one dimension (stretching) produces letterboxing or distortion. Most image editors and video tools let you "lock ratio" — the calculator gives you the target numbers to type in. And when you need those dimensions in the physical world — checking how large a 16:9 frame really displays or prints — the actual-size online ruler puts true centimeter and inch scales on your screen.
Aspect ratio is width divided by height. For 1920x1080: 1920/1080 = 1.7778, which simplifies to 16:9 by dividing both sides by the greatest common divisor (120).
What is the aspect ratio of a 4K monitor?
Standard 4K (3840x2160) is 16:9 — the same as 1080p and 1440p. Ultrawide 4K (5120x2160) is 21:9, and super-ultrawide (7680x2160) is 32:9.
How do I resize an image without distortion?
Keep the aspect ratio constant. If you scale height from 1080 to 720, multiply width by the same factor: 1920 * (720/1080) = 1280. The calculator does this automatically.
Is 16:10 better than 16:9 for work?
16:10 gives ~11% more vertical space at the same width, useful for code and documents. 16:9 is better for video content since most media is mastered at that ratio.
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