Aspect Ratio Calculator
Find an image’s aspect ratio and calculate a matching dimension from a new width or height.
Try a worked example
Try a worked example
Find an image’s aspect ratio and calculate a matching dimension from a new width or height.
Check the units and options, then use the tool’s calculation button. The example is fictitious; replace its values for your own calculation.
Example input
- Original width (pixels)
- 1920
- Original height (pixels)
- 1080
- New width (optional, pixels)
- 1280
- New height (optional, pixels)
Expected output
Original dimensions: 1920 × 1080 px Aspect ratio: 16:9 New dimensions: 1280 × 720 px (height rounded to the nearest pixel)
Find the simplified width-to-height ratio and optionally calculate a matching dimension from a target width or height.
Waiting for the tool. The explanation remains available without JavaScript.
Method and limits
Enter the original width and height in pixels. To resize proportionally, enter either a new width or a new height; leave both target fields blank to see only the reduced ratio. Do not fill in both target dimensions. The matching dimension is rounded to the nearest whole pixel.
Enter positive whole-pixel dimensions and at most one target dimension. The calculated companion dimension is rounded to the nearest pixel; cropping, safe areas, and device pixel ratio are not included.
Share this tool
Only the tool’s public link is shared. Your inputs and results stay here.
Show link to copy manually
Quick answer
Find the simplified width-to-height ratio and optionally calculate a matching dimension from a target width or height.
The page and its assets load from the site; this operation uses your entered values only in this browser and does not send them to a calculation endpoint.
How to use it
Enter the original width and height in pixels. To resize proportionally, enter either a new width or a new height; leave both target fields blank to see only the reduced ratio. Do not fill in both target dimensions. The matching dimension is rounded to the nearest whole pixel.
Limits
Enter positive whole-pixel dimensions and at most one target dimension. The calculated companion dimension is rounded to the nearest pixel; cropping, safe areas, and device pixel ratio are not included.
Frequently asked questions
Can I resize based on a target height instead?
Yes. Enter either a new width or a new height to calculate the matching other dimension. Leave both blank to see only the reduced ratio; do not enter both target dimensions.
Does this crop or check an image?
No. It calculates dimensions from the numbers you enter; it does not open, crop, or inspect an image.
Why might the calculated dimensions not match the exact ratio?
Pixel dimensions must be whole numbers, so the calculated side is rounded to the nearest pixel. For example, 16:9 at 1,000 px wide is 562.5 px high, which rounds to 563 px.
Sources and references
These references document the cited standard or browser API; they do not validate the tool’s output.