Private browser utility / Calculators
Aspect Ratio Calculator
Runs entirely in your browser - no upload, no sign-up.
Presets
Resize without distortion
Result
16:9
16:9
Matching size1280 x 720
What is an aspect ratio calculator?
An aspect ratio calculator reduces a width and height to the simplest width:height relationship, such as 1920 x 1080 becoming 16:9. It also calculates the missing resized dimension so images, videos and layout boxes keep the same proportions.
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How to use
- 01Enter source dimensions
Type the original width and height in pixels or any matching unit.
- 02Read the reduced ratio
The tool simplifies the pair to the smallest width:height ratio and shows the decimal value.
- 03Resize proportionally
Enter a target width or target height. The missing dimension is calculated from the same ratio.
- 04Copy the CSS
Use the CSS aspect-ratio value in responsive layouts, cards, embeds or media containers.
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Who it's for
- Designers checking whether an image is 16:9, 4:3, 3:2, square or portrait before placing it in a layout.
- Developers copying a clean CSS
aspect-ratiodeclaration for cards, embeds and responsive media. - Video editors resizing thumbnails and frames while keeping the original proportions.
- Photographers scaling camera images for web export without distortion.
Enter any source width and height. The calculator reduces the ratio, shows the decimal width divided by height, labels the orientation, and gives a copyable CSS aspect-ratio value. Add either a target width or target height to resize proportionally without stretching.
FAQ
How do you calculate aspect ratio?
Divide the width and height by their greatest common divisor. For example, 1920 and 1080 share a divisor of 120, so 1920:1080 reduces to 16:9.
How do I resize without changing aspect ratio?
Use one known target dimension and multiply or divide by the ratio. If you know the target width, height equals target width multiplied by original height divided by original width.
What is the CSS aspect-ratio value?
CSS uses a slash form such as aspect-ratio: 16 / 9;. The calculator shows the reduced pair so you can copy it directly into a rule.
Can I use units other than pixels?
Yes. The ratio is unitless, so width and height can be pixels, inches, millimeters or any matching unit. The resize result uses the same unit you typed.
Is this aspect ratio calculator private?
Yes. All calculations run locally in your browser. No image, video or dimension data is uploaded.