Aspect Ratio Calculator

Aspect ratio calculator: get exact width and height dimensions for 16:9 video, images, and screens from any ratio. Free, private, runs in your browser.

Enter a width and height to see the reduced aspect ratio (for example 16 : 9).

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Calculation details
Every figure above is calculated locally in your browser from the assumptions shown. No inputs are sent anywhere. See the methodology section below for how this tool works.
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Planning estimate only, not financial, tax, or legal advice. Verify assumptions and current rules before making decisions.

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What does this calculator estimate?

Aspect ratio calculator: get exact width and height dimensions for 16:9 video, images, and screens from any ratio. Free, private, runs in your browser.

Euclidean GCD steps reducing 1920 by 1080 to 16:9
Euclid's mod chain finds GCD 120, reducing 1920 x 1080 to 16:9.
Transparent methodology

How this calculator works

Formula

Reduce width and height by their greatest common divisor; the ratio is width : height and the decimal value is width / height.

Worked example

1920 x 1080 reduces by GCD 120 to 16:9, or 1.778.

Sources

Frequently asked questions

What is an aspect ratio calculator and how does it work?

An aspect ratio calculator is a browser-based tool that computes the proportional relationship between the width and height of an image, screen, or design. Enter any two values (width and height, or one value plus a target ratio), and the calculator instantly returns the missing dimension or simplifies the ratio to its standard form.

Do I need to create an account or sign up to use this aspect ratio calculator?

No. This aspect ratio calculator is completely free, requires no signup, and runs entirely in your browser. Your data is never sent to a server or stored anywhere , everything is processed locally on your device for full privacy.

Can this aspect ratio calculator handle custom ratios for video, print, and web design?

Yes. The aspect ratio calculator supports standard ratios like 16:9, 4:3, and 21:9, as well as any custom ratio you enter. Simply input your desired width-to-height proportion, and it will calculate the corresponding dimensions for your specific use case.

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Cite this tool

BoringToolsKit. “Aspect Ratio Calculator.” boringtoolskit.com/aspect-ratio-calculator/. Free to reference in articles, syllabi, and answer posts with a link.

Privacy: Inputs and results stay in this browser. Any future sponsored recommendation or advertisement will be clearly labeled and kept separate from the calculation.

A worked example: reducing 1920 by 1080

Enter width 1920 and height 1080. The calculator first finds the greatest common divisor using the Euclidean algorithm: 1920 mod 1080 leaves 840, 1080 mod 840 leaves 240, 840 mod 240 leaves 120, and 240 mod 120 leaves 0, so the GCD is 120.

Dividing both sides by 120 gives 1920/120 = 16 and 1080/120 = 9, so the reduced ratio is 16:9. The decimal form is 1920/1080 = 1.7777..., displayed rounded to 1.778. Check the reduction by reversing it: 16 x 120 = 1920 and 9 x 120 = 1080, which matches the inputs exactly.

The same reduction works for awkward sizes. A 1500 by 999 image: 1500 mod 999 leaves 501, 999 mod 501 leaves 498, 501 mod 498 leaves 3, 498 mod 3 leaves 0, so the GCD is 3 and the ratio is 500:333, about 1.502. Neither number reduces further, which is exactly why the calculator reports it instead of forcing a guess at 3:2.

Where the simple ratio breaks down in practice

Non-integer inputs are the first trap. The inputs are read as Numbers, so 1280.5 by 720 is accepted and the GCD path can produce a decimal-reduced pair that no standard expresses cleanly; enter whole pixel counts when you can. Second, tiny ratios grow large: a 100 by 107 image reduces to 100:107 with a GCD of 1, which is technically exact but tells you nothing memorable.

Real workflows also round. An image scaled to fit a 16:9 box at width 1365 would need height 1365 x 9/16 = 766.5625 pixels; files store integers, so the saved height of 767 gives 1365:767, a ratio of 1.780, a drift of about 0.12 percent from true 16:9. Two files can therefore both be described as 16:9 and still differ by a pixel of height.

Finally, equal-width comparisons can mislead. A 1920 x 1280 photo is 3:2 (1.500) while a 1920 x 1080 video is 16:9 (1.778); matching either dimension alone does not match shape. Always compare the computed decimal, not the pixel width.