Converting Centimetres and Inches to Pixels for Forms and Prints

How to work out pixel dimensions from physical sizes, with worked examples for photo prints and forms that specify centimetres.

Forms and print shops often state sizes in centimetres or inches, while photo tools work in pixels. A simple formula connects them.

The formula

Pixels = size in inches × PPI

where PPI is the pixels per inch you want. For printing, 300 PPI is a common target. For screens, PPI doesn't matter as much.

Convert centimetres to inches

1 inch = 2.54 centimetres.

Inches = centimetres ÷ 2.54.

Worked examples

A 4 × 6 inch print at 300 PPI

Width: 4 × 300 = 1200 pixels
Height: 6 × 300 = 1800 pixels

A 10 × 15 cm print at 300 PPI

10 cm = 3.94 inches; 15 cm = 5.91 inches.
Pixels: about 1181 × 1772.

A passport-style photo of 3.5 × 4.5 cm at 300 PPI

3.5 cm = 1.38 inches; 4.5 cm = 1.77 inches.
Pixels: about 413 × 531.

A 2 × 2 inch photo at 300 PPI

600 × 600 pixels.

Quick reference for 300 PPI

Print size	Pixels
3.5 × 5 inches	1050 × 1500
4 × 6 inches	1200 × 1800
5 × 7 inches	1500 × 2100
8 × 10 inches	2400 × 3000
A4 (8.27 × 11.69 in)	about 2480 × 3508

If your photo is too small

If your photo has fewer pixels than needed, enlarging it will soften the result. You can print smaller, or accept a lower PPI, which is often acceptable for prints viewed at arm's length.

Aspect ratio and cropping

The print's ratio may differ from your photo's. A 4 × 6 print is 3:2, but many phone photos are 4:3. You'll need to crop, or accept white borders.

For forms that state centimetres

Some forms give a size in cm, but the upload tool wants pixels. Use 300 PPI as a convention, or check whether the form gives an example.

Screen versus print

On screens, only pixel dimensions matter. If a form asks for "3.5 × 4.5 cm", it may accept any image with that ratio, or may require specific pixels. Read the instructions.

Using your tool

Enter exact pixel dimensions in a resizer after calculating, crop to the right ratio first, and check the file size afterwards.

Try Image Compress & Resize Tool →