Aspect Ratio Calculator
Calculate image, video, screen and design aspect ratios quickly and accurately.
Enter a width and a height, and the calculator reduces them to their simplest ratio. You can also lock a ratio and resize one side to find the matching value — useful when an export has to fit an exact frame without stretching.
Quick preview
Aspect ratio
This is a shortened version. Open the full calculator for resizing, decimal ratios and common presets.
What an aspect ratio is
An aspect ratio describes the relationship between the width and the height of a rectangle, written as two numbers separated by a colon. A 1920 × 1080 video is 16:9 because both numbers divide evenly by 120. The ratio says nothing about size — a 1280 × 720 video and a 3840 × 2160 video share the same 16:9 shape.
Why the ratio matters
Displays, upload forms and print templates all expect a particular shape. When the shape does not match, something has to give: the image is stretched, letterboxed with bars, or cropped, and the crop usually takes the part you cared about. Checking the ratio before you export is faster than fixing a cropped thumbnail afterwards.
Where people use it
- Images. Keeping photos proportional when you resize them for a gallery, a product listing or a print size.
- Videos. Matching the ratio your platform expects, so footage is not pillarboxed or cut off on playback.
- Screens and displays. Comparing monitors, laptops and phones, where the same diagonal measurement can mean quite different shapes.
- Social media designs. Working out square, portrait and story dimensions before you build the artwork rather than after.
- Web design. Setting consistent hero images, card thumbnails and video embeds that hold their shape across breakpoints.
How it works
Three fields, no setup. The result updates as you type.
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Enter width
Type the width in pixels, centimetres or any unit you like. The calculator only needs the two numbers to be in the same unit.
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Enter height
Add the matching height. Decimal values work too, which helps with print measurements and design canvases.
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Get the simplified aspect ratio
The two numbers are divided by their greatest common divisor, so 1920 × 1080 comes back as 16:9 rather than 1920:1080.
Common aspect ratios
A handful of ratios cover most of what you will meet online. The shapes below are drawn to scale.
1:1
A perfect square. Common for profile pictures, product photos and grid posts where every tile has to line up.
4:3
The older television and monitor shape. Still used by many cameras, tablets, slide decks and scanned documents.
3:2
The classic 35mm photography shape, inherited by most DSLR and mirrorless cameras and by standard print sizes.
16:9
The widescreen standard for video, streaming and most laptops and monitors. 1920 × 1080 and 3840 × 2160 both sit here.
9:16
16:9 turned on its side. The full-screen vertical shape used by phone video, stories and short-form clips.
21:9
Ultrawide. Used by cinematic footage and ultrawide monitors, and often letterboxed when played on a 16:9 screen.
Why use our calculator
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Fast
The result appears as you type. Nothing is sent to a server and there is no processing wait.
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Free
No usage limits, no paid tier and no feature held back for an upgrade.
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Easy to use
Two fields and one answer. You do not need to know the formula to get the right ratio.
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No registration
No account, no email address and no sign-in wall before you can use the tool.
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Mobile friendly
The layout and the number pads work on a phone, so you can check a ratio away from your desk.
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No unnecessary setup
Nothing to install or configure. Open the page, type the two numbers, read the ratio.
Worked examples
Four sets of dimensions you are likely to run into, and the ratio each one reduces to.
| Dimensions | Aspect ratio | Typically used for |
|---|---|---|
| 1920 × 1080 | 16:9 | Full HD video, YouTube uploads, most monitors |
| 1200 × 800 | 3:2 | Camera photos, blog images, standard photo prints |
| 1080 × 1080 | 1:1 | Square social posts, avatars, product thumbnails |
| 1080 × 1920 | 9:16 | Vertical video, stories, short-form clips |
Frequently asked questions
What is an aspect ratio?
It is the proportional relationship between the width and the height of an image, video or screen, written as width:height. A 16:9 frame is 16 units wide for every 9 units tall. Two files can share a ratio while having completely different pixel dimensions.
How is aspect ratio calculated?
Divide both the width and the height by their greatest common divisor. For 1920 × 1080, the greatest common divisor is 120, and dividing both sides gives 16:9. The calculator does this step for you, including for awkward numbers that do not reduce to a familiar ratio.
What is the 16:9 aspect ratio?
16:9 is the widescreen standard used by HD and 4K video, streaming platforms and most laptop and desktop displays. 1280 × 720, 1920 × 1080 and 3840 × 2160 are all 16:9. If you are exporting video and are unsure which ratio to use, this is usually the safe default.
What is a 1:1 aspect ratio?
1:1 means the width and height are equal, producing a square. It is used for profile photos, square social posts and product thumbnails, because a square crops predictably in grid layouts and looks the same on any device orientation.
Can I calculate aspect ratio for images?
Yes. The calculator works with any width and height, so it handles photos, illustrations, screenshots and design canvases as well as video. Use your file’s pixel dimensions, which you can read from your image editor or your operating system’s file properties.
Can I use this calculator on mobile?
Yes. The page is built to work on small screens, the fields open a numeric keypad on phones and tablets, and nothing needs to be installed. If something does not behave as expected on your device, let us know.
Calculate your aspect ratio
Enter your width and height and get the simplified ratio straight away. No account, no limits.
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