How to convert centimetres to pixels
- Type a measurement in centimetres, or press one of the paper size presets.
- Set the resolution, 300 DPI for printing, 96 for anything measured on screen.
- Read the pixel result, along with the same measurement in millimetres and inches.
- For a full page, the preset also shows the complete width by height in pixels.
- Use those numbers in the image resizer to produce a file at exactly that size.
What this converter does
- Converts in both directions, type into either field and the other follows.
- Includes A4, A5, A3 and standard card presets so you do not have to look them up.
- Shows the complete page dimensions in pixels, not just a single measurement.
- Reports millimetres and inches alongside, which suits mixed-unit specifications.
- Uses the exact 2.54 centimetres per inch definition rather than an approximation.
- Updates live as you type, with no calculation button.
Metric measurements meeting a pixel grid
Most of the world specifies print in centimetres and millimetres. Almost all image software counts in pixels. Bridging the two requires a resolution figure, because a pixel has no inherent size. It only acquires one when you decide how many of them fit into a unit of physical distance.
The chain runs through inches, since DPI is defined per inch. One inch is exactly 2.54 centimetres, so the calculation is: divide centimetres by 2.54 to get inches, then multiply by the DPI to get pixels. At 300 DPI, one centimetre is about 118 pixels. This converter does both steps and rounds sensibly.
Paper sizes worth memorising
- A4: 21 × 29.7 cm, which is 2480 × 3508 pixels at 300 DPI.
- A5: 14.8 × 21 cm, or 1748 × 2480 pixels at 300 DPI.
- A3: 29.7 × 42 cm, or 3508 × 4961 pixels at 300 DPI.
- Business card: commonly 8.5 × 5.5 cm, giving 1004 × 650 pixels at 300 DPI.
The A series has a pleasing property: each size is exactly half the previous one, folded across the long edge, and every size shares the same aspect ratio of one to the square root of two. That is why scaling artwork between A4 and A3 never distorts anything.
Remember the bleed
Anything printed to the edge of the paper needs bleed, extra artwork extending beyond the trim line, so that a slight misalignment in cutting does not leave a white sliver. Three millimetres per edge is the usual requirement in metric printing.
That means a full-bleed A4 document is not 21 by 29.7 centimetres of artwork but 21.6 by 30.3, since 3 mm is added on all four sides. At 300 DPI that works out to 2551 by 3579 pixels rather than 2480 by 3508. Supplying artwork without bleed is one of the most common reasons a print job gets sent back, so check your supplier's specification before exporting.
Choosing the resolution honestly
300 DPI is the default for a reason: it matches what the eye can resolve at normal reading distance, and it is what commercial printers expect. Going higher rarely improves anything visible while multiplying the file size, 600 DPI quadruples the pixel count for a difference most people cannot see outside fine line art.
Going lower is often perfectly fine. A poster viewed from two metres looks sharp at 150 DPI, and a large banner at 100 or less. The right question is not "what is the highest quality" but "how close will anyone be standing". To check whether an image you already have is sufficient, the DPI calculator works the problem from the other end, and the pixels to inches converter handles imperial specifications.
Turning the numbers into a file
Once you know the pixel dimensions you need, the image resizer will produce them with the aspect ratio locked. If the source is vector artwork, exporting at the target size with the SVG converter gives a genuinely sharp result at any scale, because the shapes are redrawn rather than enlarged.