About this calculator
Find the ratio of a size, or the new height for a new width.
How to use it
- Choose what to find.
- Enter width and height.
- Enter a new width to resize.
The formula
Ratio = width ÷ gcd : height ÷ gcd; new height = new width × height ÷ width
- gcd
- greatest common divisor
Worked example
1920 × 1080
- Both divide by 120: 16:9, widescreen.
- At 1280 wide, the height is 720.
What the result means
Reels and Shorts use 9:16; Instagram posts use 1:1 or 4:5.
Assumptions
- Pixel sizes.
Limitations
- Some displays use non-square pixels.
Frequently asked questions
What ratio is 1920 × 1080?
16:9.
What size is a 9:16 video?
1080 × 1920 pixels is common.
How do I resize without stretching?
Keep the same ratio: new height = new width × old height ÷ old width.
Last reviewed on 3 October 2026. Found a mistake? Tell us.