Pixel Aspect Ratio Calculator

Pixel aspect ratio describes the shape of one pixel as displayed. A ratio of 1:1 means square pixels, which is standard for modern computer graphics, web images, and most high-definition video. Older television and digital-video formats often store rectangular pixels. Their encoded frame dimensions therefore do not directly equal the proportions viewers see on screen. Three ratios describe this relationship. Storage aspect ratio is the stored pixel width divided by pixel height. Display aspect ratio is the intended physical width divided by physical height, such as 4:3 or 16:9. Pixel aspect ratio links them: display aspect ratio equals storage aspect ratio multiplied by pixel aspect ratio. Rearranging gives PAR = display width × pixel height divided by display height × pixel width. For example, a 720 by 480 frame has a storage ratio of 3:2, but it may be intended for 16:9 presentation. Its pixels must be wider than square so the displayed image expands horizontally. Multiplying stored width by the calculated PAR gives an equivalent square-pixel display width. Editing software may use standardized rational values that differ slightly from a simple frame-level calculation because standards account for clean aperture and historical sampling conventions. Correct interpretation prevents circles from appearing oval and people from looking unnaturally narrow or wide. Media metadata normally tells a player how to scale the image, but metadata can be missing, incorrect, or discarded during transcoding. The calculator helps diagnose such footage and choose a square-pixel conversion size. It does not resample the image or change the source file. Keep storage, pixel, and display ratios distinct when preparing assets. For a new square-pixel image, PAR should be 1 and storage ratio should match display ratio. For archival or broadcast video, preserve the authoritative format metadata rather than guessing from resolution alone. When converting, use a high-quality scaler, select a practical integer output dimension, and verify the result against known geometry or production documentation. Small differences caused by rounding are normal, but unexplained large differences usually indicate the wrong target display ratio.