DPI (dots per inch) and PPI (pixels per inch) both describe how much detail fits in one inch of a physical medium. For digital images destined for print, PPI measures the pixel density at a given print size — and 300 PPI is the professional standard. Below 150 PPI, pixelation becomes visible at normal reading distance (~30 cm).
The formula
PPI (pixels per inch) at a given print size:
PPI = pixel_width / print_width_inches
PPI = pixel_height / print_height_inches
(Use whichever dimension you know. Both should give the same value
if the image and print dimensions share the same aspect ratio.)
Maximum quality print size at 300 PPI:
max_print_width_in = pixel_width / 300
max_print_height_in = pixel_height / 300
Practical examples
Example 1 — Can I print a phone photo at 8×10 inches? A 12 MP smartphone captures ~4000×3000 px. At 8×10: PPI from width = 4000/8 = 500 PPI — well above 300. You can print larger; maximum at 300 PPI: 4000/300 = 13.3 in wide, 3000/300 = 10 in tall.
Example 2 — Magazine ad at 300 PPI. The ad is half a page: 3.75 × 4.75 in. Required pixels: 3.75 × 300 = 1125 px wide × 4.75 × 300 = 1425 px tall = 1,603,125 total pixels (~1.6 MP). A modern smartphone camera covers this easily.
Example 3 — Large-format banner at 72 PPI. A 6×3 foot banner viewed from 3 meters. At 72 PPI: 72 × 12 in/ft = 864 px per foot × 6 ft = 5184 px wide × 3 ft × 864 = 2592 px tall. At 50 PPI (acceptable for banners): 3600 × 1800 px.
Common mistakes
- Confusing DPI with PPI. PPI is an image property (pixels per inch at a given print size). DPI is a printer property (ink dots per inch). A 1200 DPI laser printer uses many dots to reproduce each pixel — the concepts are related but not the same quantity.
- Setting the DPI in image metadata rather than calculating it. Many people "set the image to 300 DPI" in Photoshop without changing the pixel count. This only changes the metadata number — the actual pixel density at print time still depends on the print size chosen.
- Using PPI to evaluate screen sharpness across different viewing distances. A 96 PPI desktop monitor viewed from 60 cm and a 400 PPI phone viewed from 25 cm may appear equally sharp. Retina threshold depends on viewing distance, not PPI alone.
International and regional variations
| Context | Typical PPI / DPI | Notes |
|---|---|---|
| Professional photo print (books, magazines) | 300 PPI | Industry standard; visible quality degradation below 200 |
| Newspaper print | 150–200 PPI | Newsprint absorbs ink; 200 is typical for quality papers |
| Large-format banner (viewed ≥ 1 m) | 72–150 PPI | Lower DPI acceptable as viewing distance increases |
| Outdoor billboard (viewed ≥ 10 m) | 15–30 PPI | Pixels invisible from typical viewing distance |
| Standard desktop monitor | 90–110 PPI | Windows 100% = 96 PPI; macOS 100% = 96–144 PPI |
| Retina / HiDPI display | 220–460 PPI | iPhone 15 Pro Max: 460 PPI |