How this calculator works
Three ratios describe a video frame. The storage aspect ratio is the frame width divided by the frame height, such as 1440 by 1080. The pixel aspect ratio says how wide each stored pixel is compared with its height. The display aspect ratio is what you see on screen, and it is the storage aspect ratio multiplied by the pixel aspect ratio. Square pixels have a ratio of 1, so the storage and display shapes match. Anamorphic formats squeeze a wide image into a narrower pixel grid; an HDV 1080 frame stores 1440 by 1080 but each pixel is four thirds as wide as it is tall, so the picture displays as 1920 by 1080. A display ratio within half a percent of a standard shape is reported as that shape, because broadcast formats round their pixel ratios slightly.
Formula
storage aspect ratio = pixel width / pixel height. display aspect ratio = storage aspect ratio x pixel aspect ratio. pixel aspect ratio = display aspect ratio / storage aspect ratio. Equivalent square-pixel width = pixel width x pixel aspect ratio.
Worked example
An HDV 1080 frame is 1440 by 1080 pixels. Its storage ratio is 1440 / 1080 = 1.3333. With a pixel aspect ratio of 4/3 = 1.3333, the display ratio is 1.3333 x 1.3333 = 1.7778, which is 16:9, and the equivalent square-pixel width is 1440 x 4/3 = 1920 pixels. Going the other way, a 704 by 480 frame displayed at 640 by 480 has a display ratio of 1.3333 and a storage ratio of 1.4667, so its pixel aspect ratio is 1.3333 / 1.4667 = 0.9091.
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Frequently asked questions
What is the difference between SAR, PAR and DAR?
SAR is the storage aspect ratio from the pixel dimensions, PAR is the pixel aspect ratio of each individual pixel, and DAR is the display aspect ratio on screen. DAR equals SAR multiplied by PAR. Confusingly, some video tools use SAR to mean sample aspect ratio, which is the same idea as PAR.
Why does 720 by 480 not display as 3:2?
A standard definition NTSC frame has non-square pixels and includes padding. The active picture is about 704 by 480 with a pixel aspect ratio near 10/11, which displays as 4:3. Treating 720 by 480 as square pixels gives 3:2 and stretches faces sideways.
How do I fix a video with the wrong pixel aspect ratio?
Set the clip pixel aspect ratio to match the format, or use a conform or scale step that changes the display shape without resampling the picture. If the video is already encoded, re-encoding with the correct display aspect ratio metadata can fix playback without changing the stored pixels.
Do modern cameras use square pixels?
Most do. Phone, mirrorless and cinema cameras record square pixels, and many modern codecs store the display aspect ratio explicitly. Anamorphic lenses are a deliberate exception: they squeeze a wide image onto the sensor and the footage is stretched back on display.