Aspect Ratio Calculator
Simplify an aspect ratio such as 1920 × 1080 to 16:9 and resize while keeping proportions.
Your inputs
Results
Aspect ratio
16:9
- As a decimal
- 1.7778 : 1
- Height for the new width
- 720
✓Exact calculation — rounded only for display
What this calculator does
Keeping the aspect ratio when resizing avoids stretched or squashed images and video. Simplify any width and height to a ratio and compute matching dimensions.
Formula and method
Ratio = width ÷ gcd : height ÷ gcd; new height = new width × height ÷ width
Worked example
Calculated by this tool with its default inputs:
Inputs
- Original width: 1920
- Original height: 1080
- New width (to find the height): 1280
- Or new height (to find the width):
Results
- Aspect ratio: 16:9
- As a decimal: 1.7778 : 1
- Height for the new width: 720
How to read the results
Common ratios: 16:9 video, 4:3 classic, 21:9 ultrawide.
Assumptions and limitations
- Non-integer sizes are shown as a decimal ratio.
Questions
Is 3440 × 1440 21:9?
It simplifies to 43:18, marketed as 21:9.
Methodology and verification
- Result type
- Exact mathematical calculation (rounded only for display)
- Formula version
- 1.0
- Automated verification
- 3 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
- Editorial review
- Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.
Privacy
Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Inputs are added to a share link only if you choose to include them. Privacy policy