The short version
PPI describes image pixels per physical inch; DPI describes printer dots per inch. They are often used loosely, but image-to-print size calculations should use PPI.
What matters most
- Pixels are image samples; printer dots are physical marks.
- One pixel may be reproduced with multiple ink dots.
- Pixel dimensions remain the primary measure of digital image information.
How to apply it
- Read the image's pixel dimensions.
- Choose a target print size.
- Divide pixels by inches to calculate PPI.
- Let the printer driver or print service handle device-specific dot patterns.
Reference table
| Term | Measures | Example |
|---|---|---|
| PPI | Image pixels per inch | 3000 pixels across 10 inches = 300 PPI |
| DPI | Printer dots per inch | A printer may place many ink dots per image inch |
| Pixel dimensions | Digital grid | 3000 × 2400 pixels |
| Megapixels | Total pixels | 7.2 MP |
Use exact dimensions and units in production notes; familiar labels can describe more than one standard.
Common mistakes to avoid
- Using printer DPI as the number of required image pixels.
- Believing 72 versus 300 in metadata changes the image when pixel dimensions stay fixed.
- Ignoring viewing distance and print process.
Continue with the right tool
Use a calculator to check the numbers against your own source and destination instead of relying on a generic preset.
Related guides
Image Resolution for Print: How Many Pixels Do You Need?
Calculate print resolution from inches and PPI, choose a realistic density and avoid unnecessary upscaling.
Print and densityWhat Is DPI? Printer Resolution Without the Common Myths
Learn what dots per inch means for printers, how it differs from image pixels and why a DPI metadata value alone does not change quality.
Print and densityWhat Is PPI? Pixels per Inch Explained for Screens and Prints
Understand pixels per inch, calculate print density and distinguish image PPI from screen pixel density and printer DPI.
Frequently asked questions
Is 300 DPI the same as 300 PPI?
People often say so, but technically the first refers to printer dots and the second to image pixels.
Does changing 72 PPI to 300 PPI improve quality?
Not unless resampling adds pixels. Without resampling it only changes the implied physical size.
Which value should a photographer calculate?
Pixel dimensions and PPI for the intended print size.