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How many pixels do I need to print a photo at 10x15 cm and 300 DPI?

Divide each side in centimeters by 2.54 and multiply by 300: a 10 by 15 cm print needs about 1181 by 1772 pixels. Type both numbers into the tool with 'Fill and crop' to avoid distortion. The tool sets pixels only and does not write a DPI value into the file, so the physical size on paper is set in the print dialog or given to the print shop.

Published · 3 min read

The calculation, step by step

DPI means dots per inch, and an inch is 2.54 cm. So the pixels needed along any side are its length in inches multiplied by the resolution.

Worked example

Short side: 10 ÷ 2.54 × 300 = about 1181 px.

Long side: 15 ÷ 2.54 × 300 = about 1772 px.

If the print shop accepts 150, roughly half is enough: 591 × 886 px.

300 is a common figure for prints held in the hand and viewed up close, but not every print shop asks for it. Ask the shop what resolution it works at before you start.

The paper's ratio is not the camera's

A 10 by 15 print has a 2:3 ratio, while phone photos are usually 3:4. Type both numbers with 'Stretch' and the picture gets slightly squashed, so choose 'Fill and crop' and the tool trims a small strip to match the ratio.

Worked example

A 4032 × 3024 landscape phone photo to 1772 × 1181 with 'Fill and crop': 4032 × 2687 of it is used, so 168 px go from the top and 168 px from the bottom.

A 3024 × 4032 portrait photo to 1181 × 1772: 168 px go from each side.

A small 1600 × 1200 photo to 1772 × 1181: it needs enlarging, so a warning appears.

Watch the orientation: for a landscape photo put the larger number in the width, for a portrait photo put it in the height. If the trimmed strip holds something important, crop the photo at 2:3 in the Image cropper and choose the position yourself.

The steps

  1. Work out the pixels from the size and the resolution your print shop wants.
  2. Open the Image resizer and choose the original photo at the highest resolution you have.
  3. Untick the ratio lock, type both numbers to match the photo's orientation, and choose 'Fill and crop'.
  4. Save as JPEG at a high quality such as 90 or above; print shows compression flaws more than a screen does.
  5. In the print dialog choose 10 by 15 paper, or send the file to the shop and state the size in centimeters.

Common questions

Why is there no DPI field in the tool?

Because the tool works in pixels only. A DPI value is just a descriptive number in the file; what really decides print quality is the number of pixels compared with the paper size.

My photo is smaller than needed. Will enlarging fix it?

Enlarging reaches the number but adds no detail, so the print may look soft. Try a smaller paper size, or a lower resolution if the shop accepts it.