Poster Size Calculator

Standard poster sizes

The A series covers most of the world: A3 at 297 by 420 millimetres, A2 at 420 by 594, A1 at 594 by 841, A0 at 841 by 1189. Each is double the area of the one below.

The US uses inch sizes with no consistent relationship: 11 by 17, 18 by 24, 24 by 36. A design laid out for one does not scale to another without cropping or margins.

The B series exists alongside A and is less common in consumer printing, sitting between A sizes. It appears in poster advertising and in some book formats.

Resolution at poster distance

Posters are viewed from further away than held material, so 150 DPI is generally sufficient and 100 DPI is acceptable for large sizes viewed across a room.

An A1 poster at 150 DPI needs 3508 by 4967 pixels. At 300 DPI it would need 7016 by 9933, which is a 70 megapixel file for no visible improvement at the distance a poster is read from.

The exception is fine text. A poster with body copy that someone will stand close to read needs the resolution the text requires rather than the resolution the images require, which is an argument for keeping text as vector rather than raster wherever the workflow allows.

Type sizes that work at distance

The rule of thumb is roughly one inch of letter height for every ten feet of viewing distance, or 25 millimetres per three metres.

A headline meant to be read from five metres therefore needs letters around 40 millimetres tall, which on an A1 poster is a substantial proportion of the height.

Which is why effective posters carry very little text. A hierarchy of one large headline, one supporting line and one small block of detail is close to the maximum a poster can hold, and designs that try to include more become unreadable at every distance simultaneously.

Paper and finish

Poster stock is usually specified in grams per square metre, and 170 gsm silk or gloss is common for indoor posters. Heavier stock feels more substantial and costs more to print and post.

Gloss gives saturated colour and reflects, which is a problem under directional lighting. Silk is a compromise. Matt reduces glare and slightly mutes the colour.

For anything going outdoors or being handled, laminate or synthetic stock is the practical choice. Standard paper outdoors fails quickly, and the cost difference is small relative to reprinting.

Mounting and display

How a poster will be displayed affects the file. Framed posters lose a few millimetres under the mount. Posters in snap frames lose a similar amount under the frame edge.

Roll-up banners have a section at the bottom that disappears into the cassette, typically 100 to 200 millimetres, and content placed there is invisible. Suppliers provide a template showing it and it is regularly ignored.

The general principle is the same as bleed and safe area: find out what the display method conceals before designing, rather than after the piece is printed and something important has vanished behind an edge.

Print quantity changes the sensible approach as much as size does. A single poster is usually digitally printed, where the cost per unit is flat and there is no setup. A run of several hundred moves to litho, which has a plate cost and a much lower per-unit price, and which also has different requirements for how the file is prepared. Asking which process a supplier will use is worth doing before designing, because it affects colour handling and the tolerances the file has to hold.