Pixel to Physical Size Converter
Convert between pixels and physical size. Pixels only have a physical size once you say how tightly they are packed.
Conversion
Choose which way round you are working: from a number of pixels to a physical measurement, or from a measurement to the pixels it needs.
Height is optional — leave it blank to convert a single dimension.
Pixel density
Pixels do not have a fixed physical size. The same 1,000 pixels can be large or small depending on how tightly the pixels are packed, so this tool needs a density — PPI, pixels per inch — before it can convert anything.
How many pixels are packed into one inch of screen or paper.
Starting points
None of these is a default. Use the density of the screen or printer you are working with.
Physical size
Physical size depends on pixel density. Enter a PPI value to convert.
Why a density is required. A pixel is a unit of image data, not a unit of length. 1000 pixels is roughly 26 cm at 96 PPI and about 8.5 cm at 300 PPI. Without a density there is no honest answer, so this tool asks for one rather than assuming.
Formula and assumptions
inchesequalspixels ÷ PPI
pixelsequalsinches × PPI
Metric conversion, using 1 inch = 25.4 mm exactly
centimetresequalsinches × 2.54
millimetresequalsinches × 25.4
Assumptions
- A pixel has no physical size until a density is chosen, so this tool never converts without one.
- Pixels are assumed to be square.
- Pixel outputs are rounded to the nearest whole pixel; the exact mathematical value is shown alongside.
- The density you supply is used exactly as entered and is never adjusted.
Questions
How many centimetres is one pixel?
There is no fixed answer. A pixel is a unit of image data, not a unit of length. It only acquires a physical size once you choose a density. At 96 PPI one pixel is about 0.026 cm; at 300 PPI it is about 0.008 cm.
What density should I use?
Use the density of the thing you are working with. For a display, calculate its actual PPI from its resolution and diagonal. For print, use the density you intend to print at. Fixed conventions such as 72 or 96 PPI describe historical or CSS reference behaviour, not your specific hardware.
Why does the tool refuse to convert without a PPI?
Because any answer it produced would be invented. Tools that silently assume 72 or 96 PPI give a number that looks authoritative but usually does not describe your situation.
Is a CSS pixel the same as a screen pixel?
Not always. CSS anchors its inch to 96 CSS pixels, but on a high-density display each CSS pixel may be drawn using several physical pixels. This converter works with whichever density you supply.