Pixel Aspect Ratio Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: August 19, 2026Not 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.
Principles of Aspect Ratios: DAR, SAR, and PAR
In digital video engineering, broadcast television standards, and computer graphics, an aspect ratio describes the proportional relationship between the width and height of an image or individual pixel. Maintaining proper aspect ratio geometry prevents images from appearing distorted, unnaturally stretched, or horizontally squished.
The Fundamental Three-Ratio Video Formulation
Digital video frames are governed by the universal aspect ratio identity:
- Display Aspect Ratio (DAR): The intended physical geometric shape of the screen or display image (e.g., 16:9 widescreen or 4:3 legacy TV).
- Storage Aspect Ratio (SAR): The ratio of horizontal to vertical pixel grid resolution counts: SAR = Width Pixels / Height Pixels.
- Pixel Aspect Ratio (PAR): The geometric shape of each individual pixel: PAR = Pixel Width / Pixel Height.
Square vs. Non-Square (Anamorphic) Pixels
While modern high-definition digital formats (1080p, 4K) utilize Square Pixels (PAR = 1.0), historical standard-definition digital video (such as DVD video and D1 broadcast standards) utilized non-square rectangular pixels to fit 4:3 and 16:9 widescreen imagery into standardized broadcast resolutions:
| Video Standard | Storage Resolution (SAR) | Target Display (DAR) | Required Pixel Aspect Ratio (PAR) |
|---|---|---|---|
| NTSC Standard (4:3) | 720 × 480 (1.50:1) | 4:3 (1.333:1) | 10:11 (approx. 0.9091, tall pixels) |
| NTSC Widescreen (16:9 Anamorphic) | 720 × 480 (1.50:1) | 16:9 (1.778:1) | 40:33 (approx. 1.2121, wide pixels) |
| PAL Standard (4:3) | 720 × 576 (1.25:1) | 4:3 (1.333:1) | 59:54 (approx. 1.0926, wide pixels) |
| PAL Widescreen (16:9 Anamorphic) | 720 × 576 (1.25:1) | 16:9 (1.778:1) | 118:81 (approx. 1.4568, very wide pixels) |
| Modern HD / 4K (All) | 1920 × 1080 / 3840 × 2160 | 16:9 (1.778:1) | 1:1 (exactly 1.0000, square pixels) |
Letterboxing, Pillarboxing, and Windowboxing
When video content with one aspect ratio is displayed on a screen with a different native aspect ratio, video processors apply formatting geometry:
- Letterboxing: Black matte bars placed on the top and bottom of the display when showing wider cinematic content (e.g., 2.39:1 anamorphic movie) on a 16:9 television.
- Pillarboxing: Black vertical bars placed on the left and right sides when displaying narrower 4:3 content on a 16:9 widescreen monitor.
- Windowboxing: Black borders on all four sides occurring when 4:3 pillarboxed content is improperly scaled within a 16:9 letterbox frame.
Step-by-Step Worked Calculation Example
Example: Converting Anamorphic DVD Video to Square Pixel HD Widescreen
Problem: A digital video archiving engineer rips a standard-definition NTSC widescreen DVD frame measuring 720 × 480 pixels with a non-square PAR of 40:33 (1.2121). Calculate: (1) The true display aspect ratio; and (2) The proper square-pixel (PAR = 1.0) scaled resolution required to display the video on a web browser without horizontal squishing.
Step 1: Calculate true display aspect ratio (DAR):
DAR = (720 / 480) × (40 / 33) = (1.50) × (1.21212) = 1.8181 ≈ 16:9 (1.778 with ITU crop)
Step 2: Scale horizontal resolution to square pixels (holding vertical height constant at 480p):
Scaled Width = Stored Width × PAR = 720 × (40 / 33) = 872.72 ≈ 872 pixels
Step 3: Scale to standard 720p HD frame (holding 16:9 DAR):
Width for 720p = 720 × (16 / 9) = 1,280 pixels (1280 × 720)
Conclusion: The video should be rendered at 872 × 480 (or upscaled to 1280 × 720) in square pixels to preserve correct human body proportions.
Common Aspect Ratio Mistakes
- Ignoring PAR Metadata Flags in Video Containers: If video editing software fails to read the PAR flag in an MP4 container, it displays 720x480 at 3:2 square pixels, causing actors to appear horizontally squished.
Cinematic Anamorphic Lenses and Squeeze Factors
In theatrical motion picture production, cinematographers utilize cylindrical Anamorphic Lenses (with optical squeeze factors of 1.33x, 1.5x, 1.8x, or 2.0x) to optically compress ultra-widescreen 2.39:1 panoramic vistas onto standardized 4:3 or 16:9 camera sensors.
During post-production editing, the digital video editor applies a corresponding non-square Pixel Aspect Ratio (e.g., PAR = 2.000) to "desqueeze" the image horizontally, restoring natural organic geometry while preserving characteristic anamorphic horizontal blue lens flares and oval out-of-focus background bokeh.
Conforming Legacy Standard-Definition Footage
When remastering standard-definition legacy broadcasts (720x480 NTSC) into modern high-definition 1080p streaming formats, video restoration software must de-interlace and scale pixels from 10:11 non-square geometry to 1:1 square pixels, preventing circular objects (such as wheels and sports balls) from displaying as distorted horizontal ellipses.
Anamorphic Desqueeze in Modern Cinematography Monitors
Professional on-set cinema monitors (such as SmallHD and Atomos field recorders) feature real-time hardware anamorphic desqueeze processors, allowing camera operators and directors to preview perfectly proportioned 2.39:1 widescreen framing on a 16:9 monitor while shooting with 2.0x anamorphic prime lenses.
Clean Aperture vs. Production Aperture Standards
Broadcast television SMPTE standards define a clean aperture rectangle within the full raster frame, guaranteeing that critical graphics and captions remain visible on all consumer display televisions without edge distortion.