Aspect Ratio Calculator
Find a reduced ratio and proportional image or video dimensions
Runs in your browser · nothing is uploaded
What it does
Use the original width and height to find the simplest whole-number ratio, then choose a new width to calculate its matching height. This is useful when preparing images, presentation slides and video dimensions. The tool calculates dimensions only; it does not resize or upload an image.
How to use
- Enter the original width and height in pixels.
- Enter the desired new width and choose Calculate.
- Use the rounded height for a pixel-based image editor, or copy the precise proportional height when fractional dimensions are useful.
Calculation rules and limits
- Each dimension must be a whole number from 1 to 1,000,000.
- The ratio divides both original dimensions by their greatest common divisor.
- New height = target width × original height ÷ original width. Pixel height rounds to the nearest whole pixel.
- Rounding can introduce a small ratio difference. No crop, rotation, DPI conversion or file resampling is performed.
Example
1920 × 1080 reduces to 16:9. A target width of 1280 gives a height of 720. For a 3:2 original and width 100, the proportional height is 66.666… and the rounded height is 67 pixels.
Calculations run in your browser without uploading your calculation data. Changing an input clears the previous result; choose Calculate again to get the updated answer.
A target size whose height rounds to zero pixels is rejected; increase the target width.
FAQ
Can I use portrait dimensions?
Yes. Enter 1080 × 1920 to get 9:16. A new width of 540 produces a height of 960.
Why are two heights shown?
The proportional height may be fractional. Raster images require a whole number of pixels, so the rounded result is also shown.
Does it resize an image file?
No. It calculates dimensions only. Use an image resizer to apply the calculated width and height.
