To calculate a video’s aspect ratio, divide its width in pixels by its height. To write the result as a familiar whole-number ratio, reduce width:height by their greatest common divisor. For example, 1920 × 1080 is 16:9, while 1080 × 1920 is 9:16.
How to calculate a video’s aspect ratio
- Find the frame dimensions. Read the video’s width and height from its file metadata or media details. Keep width first and height second.
- Divide width by height. The decimal form is width ÷ height. For 1920 × 1080, 1920 ÷ 1080 = 1.777…, usually rounded to 1.78.
- Reduce the dimensions for ratio notation. Divide both width and height by their greatest common divisor. For 1920:1080, divide both by 120 to get 16:9.
Adobe describes aspect ratio as the ratio of video width to height and gives 1440 × 1080 as 1440/1080 = 1.33, corresponding to 4:3 (Adobe Experience League: Video in Dynamic Media).
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Examples: dimensions to aspect ratio
| Video dimensions | Width ÷ height | Aspect ratio |
|---|---|---|
| 1920 × 1080 | 1920 ÷ 1080 ≈ 1.78 | 16:9 |
| 1080 × 1920 | 1080 ÷ 1920 = 0.5625 | 9:16 |
| 1440 × 1080 | 1440 ÷ 1080 = 1.333… | 4:3 |
| 1080 × 1080 | 1080 ÷ 1080 = 1 | 1:1 |
A decimal above 1 means the frame is wider than it is tall; below 1 means it is taller than it is wide. The order matters: a portrait frame such as 1080 × 1920 is 9:16, not 16:9.
Where to find width and height
Check the file’s metadata or its details in a media player or editing application. Look for dimensions written as width × height, for example, 1920 × 1080. If a file has been rotated or was encoded with unusual pixel-shape metadata, the displayed orientation or shape may not be obvious from the two stored numbers alone.
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Aspect ratio is not resolution
Aspect ratio describes shape; resolution describes the pixel dimensions. A 1280 × 720 video and a 1920 × 1080 video are both 16:9, but the latter has more pixels. YouTube lists 1920 × 1080 as one resolution for its standard 16:9 computer-player ratio. Its player adapts to video dimensions and the viewer’s device, so 16:9 is guidance for that player rather than a universal requirement for every video or platform (YouTube Help: Video resolution & aspect ratios).
How to resize without distorting the picture
If you are changing dimensions while preserving the same framing, scale width and height by the same factor. For a target ratio of 16:9, calculate a missing dimension with height = width × 9 ÷ 16. For example, a 1280-pixel-wide 16:9 frame is 720 pixels high.
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When the source and target ratios differ, choose deliberately among these approaches:
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware match- Crop: remove part of the image to fill the target frame. Check that important subjects or text are not cut off.
- Pad: add borders around the image to fit it without cropping. YouTube advises against adding padding or black bars directly into an upload when its player can adapt to the video’s dimensions.
- Stretch: change width and height by different proportions. This fills the frame but distorts shapes, so it is usually not the right choice when people and objects should retain their proportions.
Before exporting, check the destination’s current upload guidance and decide whether the intended orientation is landscape, portrait, or square. Also consider how much a crop would discard and whether borders are acceptable.
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When width ÷ height may not match the displayed shape
For ordinary square-pixel video, stored width divided by stored height gives the frame’s shape. Some older or anamorphic files use non-square pixels, which can make the displayed image shape differ from the simple dimensions. FFmpeg distinguishes the display aspect ratio (DAR), the ratio of the full displayed image, from the sample aspect ratio (SAR), the ratio of individual pixels; aspect metadata and scaling or cropping filters can affect how a file is shown (FFmpeg FAQ: How do I set the Aspect Ratio?).
If a video looks stretched despite dimensions that suggest a familiar ratio, inspect its display and pixel aspect metadata rather than assuming the arithmetic is wrong.
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Common calculation and resizing problems
- The ratio seems upside down: check that you divided width by height and wrote width first. Reversing the dimensions turns landscape into portrait.
- The decimal does not look exact: many ratios produce repeating decimals. Round for a quick decimal estimate, or reduce the integer dimensions to get the exact familiar ratio.
- The resized video looks stretched: width and height may have been scaled by different factors. Preserve proportions, or intentionally crop or pad instead.
- The stored dimensions do not match the apparent shape: check for rotation or non-square pixel metadata, especially with older or anamorphic footage.
- The upload has unwanted black bars: check whether borders were added into the file. For YouTube, its player can adapt to video dimensions, and its guidance says not to bake in padding or black bars.
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