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Aspect Ratio Calculator

Simplify ratios and calculate missing width or height.

Find the ratio of a size

Resize to a ratio

Use via API

Simplify width × height to an aspect ratio (1920×1080 → 16:9, with the nearest common preset), or resize to a ratio by solving the missing width or height. Send JSON, get JSON back.

POST https://pithlab.com/api/v1/tools/aspect-ratio-calculator

curl https://pithlab.com/api/v1/tools/aspect-ratio-calculator \
  -H "Authorization: Bearer $PITHLAB_KEY" \
  -H "Content-Type: application/json" \
  -d '{"mode":"simplify","width":1920,"height":1080}'

Fields and responseOpenAPI documentGet an API key

About the Aspect Ratio Calculator

Find the aspect ratio of any width and height, simplify ratios like 1920×1080 to 16:9, and work out a missing width or height. Includes common presets.

How to use the Aspect Ratio Calculator

  1. To find a ratio, enter a width and height. The tool reduces them with the greatest common divisor and names the closest common ratio.
  2. To resize, enter or pick a ratio, then type either a new width or a new height to get the other side.
  3. Pick a preset such as 16:9, 4:5 or 9:16 to fill in the ratio, and copy the result.

Examples

Full HD

Input

1920 × 1080

Output

16:9
A laptop screen that is almost 16:9

Input

1366 × 768

Output

683:384
Height of a 1280px wide 16:9 video

Input

16:9, width 1280

Output

1280 × 720
Width of a 1350px tall 4:5 post

Input

4:5, height 1350

Output

1080 × 1350

Frequently asked questions

How do you simplify an aspect ratio?

Divide the width and height by their greatest common divisor. For 1920×1080 the GCD is 120, so the ratio is 16:9. Decimal ratios are scaled to whole numbers first, so 1.85:1 becomes 37:20.

Why is my screen 683:384 rather than 16:9?

1366×768 does not divide exactly to 16:9 (1.7786 versus 1.7778), so its exact ratio is 683:384. The calculator also shows the nearest common ratio when one is within 1%.

How do I calculate the height for a new width?

Multiply the new width by the ratio's height and divide by its width. A 1280px wide 16:9 frame is 1280 × 9 ÷ 16 = 720px tall.

Is 21:9 an exact ratio?

Usually not. Ultrawide monitors sold as 21:9 are typically 2560×1080 (64:27, about 2.37:1) or 3440×1440 (43:18, about 2.39:1).