Aspect Ratio Calculator
Aspect ratio
:
16:9
1.778 : 1
Resize keeping this ratio
Type a new width or height — the other fills in to match.
:
Find the aspect ratio of any width and height, then resize while keeping the ratio — no stretching. One-tap presets for 16:9, 4:3, 21:9 and more. Free, instant, nothing to install.
How to Use the Aspect Ratio Calculator
1
Enter width and height
Type any width and height, or tap a preset. The tool shows the simplified ratio (like 16:9) and the decimal ratio.
2
Resize to fit
Enter the new width you need and the matching height appears automatically — or enter a height to get the width — so nothing is stretched.
3
Use it anywhere
Scale photos, video frames, thumbnails, ad units or design elements to fit a space while keeping the proportions exact.
Frequently Asked Questions
How do I calculate an aspect ratio?
An aspect ratio is the width divided by the height, written as two numbers separated by a colon such as 16:9. To reduce any width and height to a clean ratio, divide both by their greatest common divisor — for example 1920 by 1080 both divide by 120, giving 16:9. This calculator does that automatically and also shows the decimal ratio.
How do I resize while keeping the aspect ratio?
Set the original width and height to define the ratio, then type the new width you want and the calculator fills in the matching height automatically — or type a new height to get the width. Because both new dimensions come from the same ratio, the image or video is never stretched or squashed.
What are common aspect ratios?
16:9 for modern TVs, monitors and most video; 4:3 for older screens and many photos; 21:9 for ultrawide and cinematic video; 1:1 for square social posts; 3:2 for many cameras and prints; and 9:16 for vertical phone video. The calculator has one-tap presets for these.
Is anything uploaded or saved?
No. The calculator runs entirely in your browser with plain arithmetic — you are only entering numbers, and nothing is uploaded, stored or shared. There is no sign-up, and it works offline once loaded, on phone, tablet or desktop.