Resize Image to Centimeters

A digital image has no physical size of its own. It is a grid of pixels, and how large it prints depends on how many of those pixels the printer puts into each inch. DPI, dots per inch, is that number. Once you fix it, every centimeter on paper corresponds to a fixed number of pixels, and the conversion is simple arithmetic.

The arithmetic rests on one exact definition: an inch is 2.54 centimeters, as set by the international yard and pound agreement and published by NIST. So at 300 DPI one centimeter holds 300 ÷ 2.54, a little over 118 pixels. The tool runs this calculation when you type a size in cm and rounds to whole pixels, because an image cannot have part of a pixel.

The table lists common print widths in whole inches with their centimeter value and the pixels they need at 300 DPI. It is handy for checking whether an image you already have is large enough before you resize it.

The DPI field appears as soon as you switch the unit to cm, mm or inches, and it starts at 300. That value is the common target for prints viewed up close, such as photos, certificates and pages in a booklet. Lower values give fewer pixels for the same size: at 150 DPI a 15 × 10 cm image is about 886 × 591 pixels, which can look slightly soft on photo paper but is often fine for a draft or a large print seen from a distance.

If an application form or a print shop names a resolution, type exactly that number. Some forms specify both a size in centimeters and a pixel range, and matching the DPI they had in mind is the easiest way to land inside it.

Phone photos are usually 4:3, while 15 × 10 cm is 3:2. When you fill in both width and height, the picture has to be fitted into a frame of a different shape. Crop to fill, the default on this page, fills the frame completely and trims what does not fit, keeping the center. That is what photo labs do, and it gives a print without white edges.

If nothing may be cut off, for example on a document scan, choose Fit inside to keep the whole image within the size, or Pad with color to fill the leftover space with white. For a print with only one fixed side, enter that side and leave the other at 0; the tool then calculates it from the original proportions.

The formula below is the whole calculation, and it works in the other direction too: divide a pixel count by the DPI and multiply by 2.54 to see how many centimeters an image will print at.

The output keeps the original format unless you pick another one under Output format. For printing, JPG at the default quality of 85 is a good balance, and PNG avoids compression entirely if the image has text or fine lines. The DPI value is stored in the file, so layout and print programs place the image at the centimeter size you typed.

If the resized image also has to stay under a file size limit, tick Limit file size and set it in KB or MB. For pure number conversions without an image, such as checking how many centimeters 600 pixels are, use the Pixel Converter page. To change only the outline of a picture without resizing it, Crop Image is the better tool.

A batch of up to 20 pictures gets the same centimeter size, which suits a set of prints for one album page or a series of product photos for a catalog. Each image is cropped around its own center, so check any picture whose subject sits near an edge, or set Crop position to keep that side.