How many DPI for printing? A short guide
DPI (dots per inch) is the number of dots per inch of print. In photography it is used interchangeably with PPI, the number of image pixels per inch. The more pixels per inch, the sharper the print. The same photo can look great as a 4 × 6 inch print and poor as a poster, because the same pixels are spread over a larger area.
The conversion is simple: print size in inches equals the number of pixels divided by DPI. Example: a 6000 × 4000 px photo at 300 DPI gives a print of 20 × 13.3 inches (51 × 34 cm). The calculator above does this automatically in both directions: from pixels to inches or centimeters, and from a print size to the resulting DPI.
300 DPI is the gallery-quality standard for prints viewed up close: albums, prints, photo books. 150 DPI is perfectly fine for prints viewed from about a metre, and large-format posters and banners are printed at as little as 72 to 100 DPI, because they are viewed from several metres away. Rule of thumb: the greater the viewing distance, the fewer DPI you need.
How many pixels is 300 DPI?
At 300 DPI every inch of print needs 300 pixels. A 4 × 6 inch print needs 1200 × 1800 px, roughly 2 MP, 5 × 7 inches needs 1500 × 2100 px and 8 × 10 inches needs 2400 × 3000 px. At 150 DPI half the pixels per side are enough: 600 × 900 px for 4 × 6 inches. The full size table is above.
How many pixels is 150 DPI?
At 150 DPI a 4 × 6 inch print needs 600 × 900 px (about 0.5 MP), 8 × 10 inches needs 1200 × 1500 px, and 11 × 14 inches needs 1650 × 2100 px (about 3.5 MP). That is enough for prints viewed from about three feet: wall photos, posters for the home, larger photo books.
How many pixels is 600 DPI?
600 DPI is twice the 300 DPI standard, so you need four times the pixels. A 4 × 6 inch print at 600 DPI needs 2400 × 3600 px (about 8.6 MP), 5 × 7 inches needs 3000 × 4200 px (12.6 MP), and 8 × 10 inches needs 4800 × 6000 px (28.8 MP). In practice 600 DPI makes sense for scans and fine details viewed up close; on an ordinary print the eye cannot tell 600 from 300 DPI.
How many pixels for A4 and A3?
A4 is 8.3 × 11.7 inches (21 × 29.7 cm), so at 300 DPI it needs 2480 × 3508 px (about 8.7 MP) and at 150 DPI 1240 × 1754 px. US Letter (8.5 × 11 inches) needs 2550 × 3300 px at 300 DPI. A3 is 11.7 × 16.5 inches: 3508 × 4961 px at 300 DPI (about 17.4 MP). Any modern camera and most phones meet this.
DPI vs PPI: what is the difference?
PPI (pixels per inch) describes the file: how many image pixels fall on one inch of print. DPI (dots per inch) describes the printer: how many ink dots it lays down per inch. Labs and print shops casually say "DPI" when they mean PPI, so this calculator uses that name too. The DPI value stored in the file (e.g. 72 or 300) changes neither the pixel count nor the quality; what matters is the ratio of pixels to print size.