What resolution do I need for an A1 poster?

Start with the finished size

A1 measures 594 × 841 mm before bleed. For each edge, divide its centimetres by 2.54 and multiply by the chosen image density. Round each result to the nearest whole pixel. The portrait figures below can be swapped for a landscape poster.

Print shops often say DPI when discussing an image file. These calculations describe pixels per inch, or PPI. A printer's ink-dot resolution is a different setting and should not be substituted directly into this formula.

Choose density for the viewing distance

An A1 print examined at arm's length exposes more detail than the same poster viewed across a room. A lower-density file may be acceptable for distant viewing, but the subject, sharpening, paper and print process all matter. A small physical proof is more useful than assuming that one density always guarantees quality.

Increasing the pixel count cannot guarantee the recovery of text, faces or texture that were never captured. Inspect an enlarged crop before ordering a full poster.

A1 pixel reference table

Figures use the nominal paper dimensions, with no bleed. If the printer asks for 3 mm bleed on every edge, calculate from 60.0 × 84.7 cm instead. Follow its template for trim marks and safe margins.

Match the image shape before enlarging

A camera photo usually has a different aspect ratio from A1. To fill the paper, crop to the final shape first; to preserve the entire photo, allow borders. PrintScale sizes the image by its long edge while preserving its proportions, so selecting 84.1 cm alone does not crop it to A1. Its current 600 DPI tool limit is 50 cm on the long edge; the 600 PPI row is a reference, not an available A1 output preset.

The print-size calculator checks the size your existing pixels support. For more on image density, see Adobe's explanation of printed image resolution.

When your crop is ready, check your photo in PrintScale.