Pixels, CM, Inches, and DPI — The Designer's Unit Conversion Guide

Common Design Unit Conversions

Pixels to Physical Size

Pixels = Physical Size (inches) x DPI

At 300 DPI (print standard):

• 1 inch = 300 px
• 1 cm = 118 px
• A4 paper = 2480 x 3508 px

At 72 DPI (legacy web):

• 1 inch = 72 px
• 1 cm = 28 px

Points and Pixels

Typography uses points (pt) as a unit:

• 1 pt = 1/72 inch
• At 96 PPI screen: 1 pt = 1.333 px
• At 72 PPI: 1 pt = 1 px

Quick Reference Table

Physical Size	72 DPI	150 DPI	300 DPI
1 inch	72 px	150 px	300 px
1 cm	28 px	59 px	118 px
2.5 cm (1 in)	72 px	150 px	300 px
3.5 cm	99 px	207 px	413 px
4.5 cm	128 px	266 px	531 px
A4 (21x29.7 cm)	595x842 px	1240x1754 px	2480x3508 px
Letter (8.5x11 in)	612x792 px	1275x1650 px	2550x3300 px

Common Paper Sizes in Pixels at 300 DPI

Paper Size	Dimensions (mm)	Pixels (300 DPI)
A4	210 x 297	2480 x 3508
A5	148 x 210	1748 x 2480
Letter	216 x 279	2550 x 3300
Legal	216 x 356	2550 x 4200
Passport photo	35 x 45	413 x 531