Calculating image size in inches or dpi from pixels using php

Question

I need to calculate an approximate image size in inches assuming 300dpi.

I have a target image size in mind, and i want to show the user if the image they have uploa

Answer 1

DPI = "dots per inch". One dot = one pixel.

300 pixels in 300 dpi: 1 inch. You can work it out :-)

Answer 2

Given that dots == pixels:

size in inches = size in pixels / dots per inch

so if you have an image that's 900 pixels wide, at 300 dpi it will be printed at 3 inches.