Aspect Ratio Calculator

How to calculate aspect ratio

Enter the original pixel width and height to find their simplest ratio. To resize, choose a target width or height; the other side follows the same proportion. Or start with a ratio and one known side. See the aspect ratio formula guide for the full derivation and cross-check.

For whole numbers, divide both dimensions by their greatest common divisor. For decimal inputs, first multiply both by the same power of ten to make them whole numbers, then simplify.

New height = new width × original height ÷ original width
New width = new height × original width ÷ original height

For a diagonal D and ratio A:B, width = D × A ÷ √(A² + B²), and height = D × B ÷ √(A² + B²). The decimal ratio is width ÷ height. Total pixels are width × height; diagonal is √(width² + height²).

Common ratios, or your own

Choose 16:9, 9:16, 4:3, 3:2, 1:1, 21:9 and additional cinema, portrait and display ratios. Custom positive ratios work too. Resolution presets populate actual dimensions; the ratio is always calculated from those dimensions.

For example, 2560 × 1080 simplifies to 64:27, not exactly 21:9. The nearest listed ratio uses the smallest absolute difference between decimal ratios; it does not replace your exact ratio. See the full 21:9 ultrawide comparison.

Two newer pages work the same arithmetic end to end: what a 16:9 to 9:16 crop actually costs in lost area, and why 21:9 never lands on whole pixels. A third shows that crop loss and letterbox coverage are the same number. A fourth follows a chain: why adding two crop losses overstates the damage, and what the real figure is. A working tool does the geometry end to end: monitor dimensions calculator turns a diagonal and a ratio into width, height, area, PPI and pixel pitch. A fixed pair answers the other question: 27 inch vs 32 inch monitor keeps both screens editable and gives every difference in inches and percent. The step down works the same way: 24 inch vs 27 inch monitor shows what the smaller screen gives up in width, height, area and pixel density. The seat side of the same question is here: tv viewing distance turns a diagonal, a ratio, a resolution and a distance into field of view, a 30°–40° distance band and the angle one pixel covers. The panel side of it is here: how wide is a 65 inch tv gives the width, height and area of any diagonal in inches and centimetres at once, and shows what 21:9 does to the same 65 inches. The step between two sizes is a separate question: 55 vs 65 inch tv puts both panels side by side and separates the 39.7% area gain from the 18.2% width gain. One size up, how wide is a 75 inch tv gives that diagonal as 65.37 by 36.77 inches and explains why public figures for the same panel differ by up to 0.65 inch. Two sizes below that, how wide is a 50 inch tv gives 43.58 by 24.51 inches and takes apart a 44.5-to-47.8-inch range whose ends both sit above the panel. One size up from the 75, how wide is an 85 inch tv gives 74.08 by 41.67 inches and takes apart a 74.0-to-74.8-inch band that turns out to be one number, rounded four ways. The smallest of the set is here: how wide is a 43 inch tv gives 37.48 by 21.08 inches and separates the 37.5 glass figures from the 37.80-to-38.20 whole-set ones, a 0.72-inch frame. Depth is the number that never comes out of a diagonal, and 65 inch tv dimensions keeps the two apart: 2 to 12.4 inches for the finished set, 56.65 by 31.87 for the glass. The same split for the size in between is here: 70 inch tv dimensions gives 61.01 by 34.32 inches for the glass and then the two numbers the public figures usually drop — depth from about 2.8 to 13 inches, and a stand that lifts the set 1.9 to 4.16 inches. For crop planning, the aspect ratio area loss calculator shows the exact retained and discarded area, crop size and per-side removal before any pixels are cut.

For production lists, the batch aspect ratio size generator enumerates exact integer pairs under width and height limits and can require even dimensions without rounding drift.

For browser layout, the CSS aspect-ratio rounding checker separates fractional CSS geometry from device-pixel candidates and measures the drift across DPR values.

For anamorphic footage, the anamorphic desqueeze aspect ratio calculator expands stored width by the lens factor, reports the final display ratio, and audits crop loss for a 2.39:1 finish.

Whole-pixel and even-pixel rounding can slightly change the output shape. The calculator shows the resulting ratio when that happens. Decimal results are displayed to six places; calculations retain browser numeric precision.