Photo print resolution: pixels, PPI and cropping

By Mohamed Elatabany · Updated 3 October 2026

Print resolution is the number of image pixels per printed inch: PPI = visible pixels ÷ printed inches. For a 4 × 6 inch print at 300 PPI, use at least 1200 × 1800 pixels after the crop. 300 PPI is a useful target, not a guarantee of a good print.

Pixel targets for common photo sizes

300 PPI examples; fractional pixel targets rounded up
Printed dimensions	Visible pixel target
1 × 1 in	300 × 300
2 × 2 in	600 × 600
2 × 3 in	600 × 900
4 × 6 in	1200 × 1800
5 × 7 in	1500 × 2100
35 × 45 mm	414 × 532

Why cropping lowers resolution

Only the part of the source image that reaches the page counts. If a 1200 × 1800 image fills a 4 × 6 print, it supplies 300 PPI. If you zoom until only a 600 × 900 region remains visible at that same size, the print has 150 PPI. The original file’s total pixel count can therefore overstate the quality of a tightly cropped print.

How Photo Print describes quality

The app calculates PPI from the visible crop and the physical area the image occupies. Its labels are:

Excellent: 300 PPI or more.
Good: 200 to below 300 PPI.
Fair: 150 to below 200 PPI.
Low: below 150 PPI.

These are the app’s quality bands, not a passport authority’s rules. Focus, motion blur, lighting, compression, ink and paper affect the result too. A blurry original remains blurry even if it has many pixels.

PPI is different from printer DPI

PPI describes image pixels across the print. DPI describes the printer’s output dots. A printer’s advertised DPI does not replace the need for enough image detail. Changing a file’s resolution label without adding real detail does not make the original photo sharper.

If the quality warning appears

Try the original camera photo rather than a screenshot or messaging copy.
Reduce crop zoom if that preserves the composition.
Choose a smaller print size if your use allows it.
Print one test and assess it at the distance it will be viewed.

Use the photo size calculator for pixel targets. It does not inspect your actual photo or validate identity-document rules.

Next steps

Written by Mohamed Elatabany, developer of Photo Print. App instructions are based on Photo Print; printer behaviour varies. Send a correction or ask for help.