Most digital images use square pixels, so the frame size alone tells you the picture’s shape. Video formats from the standard-definition era – and some modern anamorphic and camera formats – store a frame with a fixed number of pixels that are meant to be shown wider or narrower than they are tall. Three ratios describe this: the storage aspect ratio (SAR, the pixel grid, such as 720 × 480 = 3:2), the display aspect ratio (DAR, the shape the viewer should see, such as 4:3) and the pixel aspect ratio that links them, PAR = DAR ÷ SAR.
NTSC DV at 720 × 480 shown as 4:3 has PAR = (4/3) ÷ (3/2) = 8/9 ≈ 0.889 – each pixel is narrower than tall. The same frame flagged as widescreen 16:9 has PAR 32/27 ≈ 1.185. HDV stores 1440 × 1080 and stretches it to 1920 × 1080 with PAR 4/3, and a 2× anamorphic lens doubles the width again.
If editing software interprets the PAR wrongly, circles become ovals and faces look stretched. Use the display size to export square-pixel stills or to set up a sequence correctly. (Broadcast standards based on a 704-pixel active width give slightly different values, such as 10/11.)
How to use the Pixel Aspect Ratio Calculator
- Stored width (pixels)
- Stored height (pixels)
- Display aspect ratio
- Display ratio width
- Display ratio height
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
The calculator divides the frame width by the height to get the storage ratio, divides the chosen display ratio by it to get the pixel aspect ratio, and multiplies the stored width by the PAR to give the width the picture should have with square pixels.
Worked example
NTSC DV is stored as 720 × 480: SAR = 720 ÷ 480 = 1.5. Shown at 4:3, PAR = 1.3333 ÷ 1.5 = 0.8889 = 8/9, so the square-pixel picture is 720 × 0.8889 = 640 × 480. Flagged as 16:9 instead, PAR = 1.7778 ÷ 1.5 = 1.1852 = 32/27 and the picture is 853 × 480.
Common pixel aspect ratios
| Format | Stored size | DAR | PAR |
|---|---|---|---|
| NTSC DV | 720 × 480 | 4:3 | 8:9 (0.889) |
| NTSC DV widescreen | 720 × 480 | 16:9 | 32:27 (1.185) |
| PAL DV | 720 × 576 | 4:3 | 16:15 (1.067) |
| PAL widescreen | 720 × 576 | 16:9 | 64:45 (1.422) |
| HDV / XDCAM 1080 | 1440 × 1080 | 16:9 | 4:3 (1.333) |
| DVCPRO HD 720 | 960 × 720 | 16:9 | 4:3 (1.333) |
Inputs explained
| Field | What to enter |
|---|---|
| Stored width (pixels) | A number |
| Stored height (pixels) | A number |
| Display aspect ratio | Choose one: 4:3, 16:9, 1.85:1, 2.39:1 … |
| Display ratio width | A number |
| Display ratio height | A number |
What each result means
- Storage aspect ratio (width ÷ height) = [Stored width (pixels)]÷[Stored height (pixels)]
- Pixel aspect ratio (PAR) = [D]÷([Stored width (pixels)]÷[Stored height (pixels)])
- Pixel aspect ratio as a fraction = [Pixel aspect ratio (PAR)]
- Display width with square pixels = [Stored width (pixels)]×[Pixel aspect ratio (PAR)]
- or display height with square pixels = [Stored height (pixels)]÷[Pixel aspect ratio (PAR)]
- Display aspect ratio (decimal) = [D]
Formula
Storage aspect ratio SAR = pixel width ÷ pixel height · Pixel aspect ratio PAR = DAR ÷ SAR · Display width (square pixels) = pixel width × PAR
Worked example
Inputs — Stored width (pixels): 720; Stored height (pixels): 480; Display aspect ratio: 4:3.
Results — Storage aspect ratio (width ÷ height) = 1.5; Pixel aspect ratio (PAR) = 0.8889; Pixel aspect ratio as a fraction = 8/9; Display width with square pixels = 640 px; or display height with square pixels = 540 px; Pixel shape = Narrow pixels – squeeze horizontally; Display aspect ratio (decimal) = 1.3333.
Key terms
- Pixel aspect ratio (PAR)
- Width of a pixel divided by its height.
- Storage aspect ratio (SAR)
- Number of stored columns divided by rows.
- Display aspect ratio (DAR)
- Shape of the picture as displayed; DAR = SAR × PAR.
- Anamorphic
- Recording a squeezed image that is stretched back on display.
Frequently asked questions
What is the pixel aspect ratio of NTSC DV?
720 × 480 shown at 4:3 gives 8:9 (0.889) by this simple method; the ITU-based convention used by many editors gives 10:11 (0.909).
What is the PAR of PAL DV?
720 × 576 at 4:3 gives 16:15 (1.067); at 16:9 it gives 64:45 (1.422).
What is the PAR of HDV 1080?
1440 × 1080 at 16:9 gives 4:3 (1.333), stretching it to 1920 × 1080.
What is the difference between PAR, SAR and DAR?
SAR is the shape of the pixel grid, DAR the shape the picture should have, and PAR the shape of each pixel; DAR = SAR × PAR.
Do modern cameras use non-square pixels?
Rarely for normal video, but anamorphic modes (for 1.33× or 2× anamorphic lenses) record with non-square display flags.
Why do my videos look stretched?
The software is ignoring or misreading the PAR flag. Set the sequence or export to the correct pixel aspect ratio, or resample to square pixels.