Aspect Ratio Calculator

What This Tool Calculates

This calculator solves one equation: given a known width-to-height ratio, find the missing dimension when you scale up or down. It simplifies the ratio you enter using the greatest common divisor, so 3000x2000 reduces to 3:2, and 1920x1080 reduces to 16:9.

Worked Example

Start with a 3000 x 2000 pixel photo (a 3:2 ratio, since gcd(3000, 2000) = 1000). To resize it to a new width of 1500 pixels while keeping the same shape, the tool multiplies 1500 by the height/width ratio: 1500 x (2000 / 3000) = 1500 x 0.6667 = 1000. The resized image is 1500 x 1000, and the ratio display still reads 3:2.

Using the Presets

The dropdown fills in six ratios used in video and print work: 16:9 (HD/4K video), 4:3 (older TV and slide formats), 1:1 (square social posts), 21:9 (ultrawide monitors), 9:16 (vertical mobile video), and 3:2 (standard photo prints). Selecting one overwrites the width and height fields directly.

What the Two Rectangles Show

The visual comparison scales both boxes to fit a 150px bounding area, so you can compare how a 21:9 crop looks next to a 4:3 crop without doing the math yourself.

Rounding and Scope

Results round to two decimal places, which matters if you're calculating print dimensions in inches rather than whole pixels. The tool does not convert between units (pixels, inches, cm) - it only preserves a ratio between two numbers, whatever unit you're using consistently on both sides.