Pixel-to-centimetre conversion is meaningful only when you also fix the pixel density. This tool starts from a DPI (dots per inch) and applies the textbook formula: cm = pixels ÷ DPI × 2.54. Presets cover the most common cases — 96 DPI for standard monitors, 144 and 192 DPI for Retina scaling factors, plus iPad and iPhone densities — and you can drop in any custom value.
Web layouts use a CSS reference pixel where 96 px equals 1 inch by definition, so for screen design you can almost always leave DPI at 96. Print, signage, and embedded displays are different: use the manufacturer's actual pixel density. On high-DPI screens that report a device pixel ratio, divide hardware pixels by the DPR before converting if you need CSS-pixel units instead.
Pixels are not a physical unit — their physical size depends on the screen's pixel density (DPI). 96 pixels at 96 DPI is one inch (2.54 cm). The same 96 pixels on an iPhone's 326 DPI screen is only about 0.75 cm wide.
CSS treats 96 px as 1 inch by definition (the "reference pixel"), regardless of the actual screen. For purely web work, leave DPI at 96. For print or physical signage, use the target device's real DPI.
High-DPI devices use a device pixel ratio: an iPhone "CSS pixel" still maps to 1/96 of an inch, but each CSS pixel is rendered using multiple hardware pixels. This tool converts hardware pixels — divide by your DPR if you want CSS pixels.
Yes within the floating-point precision of the browser. The math is px ÷ DPI × 2.54 cm. The only approximation is the DPI value itself — manufacturer-stated DPIs are nominal and can vary slightly between units.
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