How to use the Pixel Aspect Ratio Calculator
Enter the stored size
Stored width and height are the pixel grid, such as 1440 and 1080.
Type any field
Change the stored size or the display ratio. PAR updates as you type.
Read PAR
The big number is display shape divided by the stored shape.
Summarize with
PAR, DAR and SAR
Stored aspect (SAR) is W/H of the pixel grid. DAR is what the audience should see. PAR = DAR ÷ SAR. On modern 1920×1080, PAR is 1:1 (square pixels).
ITU-R BT.601 sampled 720×480 with non-square pixels so the displayed 4:3 picture did not match 720/480 = 3:2. Industry documents also mention 10:11 for NTSC 4:3; that is a specification choice around clean-aperture, not the naive 8:9 of 720×480 + DAR 4:3. This page shows the naive formula and notes the 10:11 convention.
Worked PAR examples
1440×1080, DAR 16:9 → PAR 4:3 (1.333). 720×480, DAR 4:3 → PAR 8:9 (0.889). Both are fixtures.
Common mistakes
Feeding the displayed size instead of the stored size.
Assuming every HD file is anamorphic. Most 1920×1080 files are square pixels.
When PAR still matters
Anamorphic HD (1440×1080 with DAR 16:9) still appears in older broadcast files. The fixture PAR 4:3 is the naive DAR÷SAR result. NTSC DV 720×480 with DAR 4:3 yields PAR 8:9 in the same formula; some documents prefer 10:11 after clean-aperture. This page shows both notes so you do not “fix” a file that was already tagged correctly.
Modern 1920×1080 YouTube uploads should stay at PAR 1:1. If a player looks skinny, check the container flags before you resample.
When PAR is 1:1
Almost every 1920×1080 file you download today has square pixels. PAR 4:3 on 1440×1080 anamorphic HD and PAR 8:9 on 720×480 are the fixtures because those are the leftover non-square cases. If DAR equals stored W/H, PAR simplifies to 1:1 and you can stop.
BT.601 also discusses 10:11 for NTSC 4:3 clean aperture. That is a spec choice, not the naive 720×480 ÷ 4:3 result of 8:9. This page shows the naive formula and points at 10:11 so you do not think the site “got NTSC wrong.”
Frequently asked questions
What is a pixel aspect ratio calculator?
It returns PAR from stored W×H and a target DAR.
Why 4:3 PAR on 1440×1080?
DAR 16:9 divided by 1440/1080 (4:3) is 4:3.
Why 8:9 on 720×480?
DAR 4:3 divided by 3:2 is 8:9.
What about 10:11?
BT.601-related practice for NTSC 4:3; it is not the naive 720×480 result.
Does YouTube need PAR?
Upload square-pixel 16:9 unless you know you have anamorphic footage.