How is this different from just dividing width by height?

Dividing gives a single decimal number (like 1.7778), useful for comparison, but the simplified whole-number ratio (16:9) is what's conventionally used to name and describe standard formats.

Can I use this for print dimensions instead of pixels?

Yes — the ratio math is unitless, so it works identically whether your width and height are in pixels, inches, centimeters, or any other consistent unit.

What if I want to scale by height instead of width?

Enter the new value in the 'scale to a new width' field using whichever dimension you're targeting — since it's a straight ratio, you can treat the labeled 'width' field as whichever dimension you actually want to fix, and read the other one from the result.

Does it save my width and height if I refresh the page?

Yes — like this site's CSS Unit Converter, the values are stored in the URL, so refreshing or sharing the link preserves exactly what you entered.

What happens if I enter a height of 0?

It doesn't error — it shows a '1:0' simplified ratio and a decimal ratio of 0, both mathematically degenerate results rather than a true ratio, since a real width:height ratio needs a nonzero height.

Can I enter a decimal width or height, like 19.5?

Yes — both the ratio simplification and its underlying GCD calculation round to the nearest whole number internally, so a decimal input still produces a valid simplified ratio.

Does scaling work in both directions — smaller as well as larger?

Yes — entering a new width smaller than the original scales the height down proportionally the same way a larger new width scales it up.

Can I try several different scaled widths quickly without re-entering my original dimensions?

Yes — changing the 'scale to a new width' field recalculates the matching height instantly; your original width and height stay put.

Aspect Ratio Calculator

About the Aspect Ratio Calculator

Simplifies a width/height pair into its lowest-terms ratio (like 1920×1080 → 16:9), and scales a dimension to a new size while preserving that exact ratio.

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How to use it

Enter a Width and Height.
Read the simplified ratio and decimal ratio in the result panel.
Enter a new Width to see the matching Height that preserves the same ratio.

Formula

Simplified ratio = width ÷ GCD(width, height) : height ÷ GCD(width, height), where GCD is the greatest common divisor of the two values (computed via the Euclidean algorithm)
Scaled height = (new width × original height) ÷ original width

Worked example

1920×1080 simplifies to a 16:9 ratio (1.7778:1) — scaling to a new width of 1280px keeps that exact ratio at 720px tall, the standard 720p resolution.

Common aspect ratios

Common aspect ratios
Ratio	Decimal	Common use
1:1	1.0000	Square — social media posts, album art
5:4	1.2500	Older monitors, some print formats
4:3	1.3333	Classic TV/monitor, older photography
3:2	1.5000	35mm film, most DSLR photos
16:10	1.6000	Laptop/monitor displays
16:9	1.7778	Widescreen video, HDTV, YouTube
21:9	2.3333	Ultrawide monitors, cinematic video
9:16	0.5625	Vertical/mobile video (Reels, Shorts, Stories)

Recommendations

• Common video/display ratios are recognizable once simplified — 16:9 (widescreen), 4:3 (older TVs/monitors), 21:9 (ultrawide), and 1:1 (square) are the ones you'll see most often.
• The GCD-based simplification is exact — no rounding — so the simplified ratio always represents the original dimensions precisely, unlike a decimal approximation.
• For print or physical media, the same ratio math applies regardless of unit (inches, cm, pixels) — the ratio itself is unitless.

Frequently asked questions

Not every real-world image or video has been shot or cropped to a standard ratio — the simplified result is mathematically exact for whatever dimensions you entered, even if it doesn't match a common named ratio.

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