Aspect Ratio Calculator
Turn any width and height into a simplified aspect ratio, lock a preset like 16:9 to auto-compute the other dimension, and browse common resolutions.
Processed locally in your browser — nothing is uploaded.
Aspect Ratio Calculator
Results
- Simplified ratio
- 16:9
- Decimal
- 1.7778
Width divided by height.
About Aspect Ratio Calculator
Enter a width and height to get the simplified whole-number ratio (via greatest common divisor) and its decimal form. Lock one of the preset ratios — 16:9, 4:3, 21:9, 1:1, 3:2, or 9:16 — and editing either dimension recomputes the other automatically.
A locked preset also shows its common real-world resolutions, from VGA up to 4K, so you can jump straight to a standard size.
Common uses
- Resize a video thumbnail while keeping 16:9
- Work out what height a 1200 px-wide 3:2 image needs
- Check what ratio an odd image size actually is
Example
Input
1920 × 1080
Output
16:9 · decimal 1.7778
Limitations
- Ultrawide "21:9" monitor resolutions are exactly 64:27, so they will not simplify to 21:9
Frequently asked questions
How do I work out the aspect ratio of an image from its dimensions?
Divide both width and height by their greatest common divisor. For 1920 × 1080 the GCD is 120, giving 16:9; this tool does the reduction for you and also shows the decimal form (1.7778).
What resolution is 16:9 for a given width?
Multiply the width by 9/16 to get the height — a 1280 px-wide 16:9 image is 720 px tall. Lock the 16:9 preset here and typing either dimension fills in the other automatically.
Why doesn't my ultrawide monitor simplify to 21:9?
Because "21:9" is marketing shorthand: 2560 × 1080 reduces to exactly 64:27 and 3440 × 1440 to 43:18, both close to but not equal to 21:9 (which would be 7:3). The calculator reports the true simplified ratio.
Are the dimensions I enter sent over the network?
No. The ratio math is a few lines of arithmetic that run in your browser; nothing you type is transmitted or logged.