A4 at 72 DPI is 595 × 842 pixels

A4 (210 × 297 mm) at 72 DPI is 595 × 842 pixels, which is 0.5 megapixels.

Portrait595 × 842 pixels
Landscape842 × 595 pixels
With 3 mm bleed612 × 859 pixels
Megapixels0.5
Aspect ratio1.42:1 (1 to √2 before rounding)
File size1.4 MB as uncompressed 8-bit RGB; a JPEG or PNG is smaller
Paper size210 × 297 mm (8.27 × 11.69 in)

The working

Pixels are inches multiplied by the resolution, and an inch is 25.4 mm.

Bleed is extra image past the trim line, so that a cut that lands slightly off still leaves ink to the edge. Print shops usually ask for 3 mm on every side of an A-series page, which makes the file 612 × 859 pixels.

Is your photo big enough?

To fill A4 at 72 DPI an image needs at least 595 × 842 pixels. Cropped to fill the sheet:

At 72 DPI the pixels of a print blend together from about 47.7 inches (121 cm) away. 72 DPI is the old screen convention: early Macintosh displays showed 72 pixels to the inch, matching the 72 points in an inch of type. Many image files still carry a 72 DPI tag for that reason.

A4 at other resolutions

ResolutionPixelsWith bleedMegapixelsUncompressed
72 DPI595 × 842612 × 8590.51.4 MB
96 DPI794 × 1123816 × 11450.892.6 MB
100 DPI827 × 1169850 × 11930.972.8 MB
150 DPI1240 × 17541276 × 17892.26.2 MB
200 DPI1654 × 23391701 × 23863.911 MB
240 DPI1984 × 28062041 × 28635.616 MB
300 DPI2480 × 35082551 × 35798.725 MB
400 DPI3307 × 46773402 × 47721544 MB
600 DPI4961 × 70165102 × 715735100 MB
1200 DPI9921 × 1403110205 × 14315139398 MB

Other sizes at 72 DPI

A4 is the standard page for letters and documents everywhere outside North America. See A4 in pixels at every resolution or everything at 72 DPI.