Print Quality Depends on DPI, Not Pixel Count Alone
The key difference between screen images and print images is how many dots are placed per inch (DPI). The same pixel dimensions printed at a larger size results in a lower effective DPI, producing visible dots and a low-quality result.
Required pixel resolution is calculated as (print size in cm ÷ 2.54) × DPI. Multiplying by channel count for the color mode (3 for RGB, 4 for CMYK) estimates the uncompressed file size.
Choosing the Right DPI
Prints viewed from a distance, like subway ads or large banners, work fine at 150 DPI. Items viewed up close, like brochures or business cards, need 300 DPI or more to avoid visible dots. High-quality photo books or art prints should consider up to 600 DPI.
Why RGB and CMYK File Sizes Differ
Work is typically done in RGB (3 channels) on screen, but files are converted to CMYK (4 channels) before printing. That extra channel adds roughly 33% to file size, so estimating it ahead of time helps plan storage and file transfer to the print shop.
Frequently Asked Questions
300 DPI is the minimum threshold where dots become invisible to the eye. Distance banners are fine at 150 DPI.
CMYK's 4 channels store more data per pixel than RGB's 3, increasing file size by about 33%.