PPI = pixels ÷ print inches
Calculate effective print PPI
Compare horizontal and vertical PPI. Different values reveal an aspect-ratio mismatch between pixels and the target print box.
Formula and worked example
How to calculate effective PPI
Horizontal PPI = pixel width ÷ print width in inches; vertical PPI = pixel height ÷ print height in inches.
2400 px ÷ 8 in = 300 PPI and 3000 px ÷ 10 in = 300 PPI, so a 2400 × 3000 px image placed at 8 × 10 in has 300 × 300 effective PPI.
If the two axes differ, the smaller value is the limiting PPI because that axis has fewer source pixels per printed inch.
Effective print PPI describes source-image density at the placed print size. Display PPI normally uses the pixel diagonal and screen diagonal; printer hardware DPI is a separate measurement.
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