Pixel Aspect Ratio Calculator
Not Every Pixel Is a Perfect Square
Most modern displays use square pixels, so a video's stored resolution and its displayed aspect ratio line up automatically. That wasn't always true: several broadcast and DV video formats store frames using non-square pixels, which means the raw stored resolution and the intended widescreen or standard display shape don't match unless a pixel aspect ratio (PAR) correction is applied. Get the PAR wrong and footage looks stretched or squeezed even though every pixel decoded correctly.
The Formula
PAR relates the storage resolution's shape to the intended display shape:
DAR (Display Aspect Ratio) = Display Ratio Width / Display Ratio Height
PAR = DAR / SAR
Working the other direction, if PAR and the storage dimensions are known, the display aspect ratio is recovered by DAR = PAR × SAR.
Where This Calculation Matters
- Video encoding and transcoding — setting the correct PAR metadata so a video plays back at its intended shape rather than stretched.
- Editing footage from older or broadcast-standard cameras — some DV and broadcast formats store non-square pixels, and importing them without the right PAR distorts the image.
- Compositing and VFX — matching pixel aspect ratio across footage from different sources so elements combine without a visible size or shape mismatch.
- Anamorphic formats — working with intentionally non-square pixel capture (common in some cinema formats) requires tracking PAR through the entire pipeline to unsqueeze correctly on output.
Worked Examples
| Storage Resolution | Display Ratio | Computed PAR |
|---|---|---|
| 720 x 480 | 16:9 | 1.1852:1 |
| 720 x 576 | 4:3 | 1.0667:1 |
| 1920 x 1080 | 16:9 | 1.0:1 (square pixels) |
A PAR of exactly 1.0 means square pixels — the storage resolution's own ratio already matches the intended display ratio, which is the case for essentially all modern digital displays and cameras.
How to Use This Calculator
- Choose a mode: Find PAR or Find DAR.
- For finding PAR, enter Storage Width, Storage Height, Display Ratio Width, and Display Ratio Height.
- For finding DAR, enter Storage Width, Storage Height, and the known Pixel Aspect Ratio (PAR).
- Select Calculate to get the result.
Related Calculations
Working with the overall frame shape rather than individual pixel shape? Use the Aspect Ratio Calculator. Need frame timing instead of frame shape? See the Frame Rate Calculator.