Poster Size Planner

Distance decides the size

Two inputs. How far back the reader stands, in metres, and how much is on the poster — light, medium, dense.

Out comes a recommended sheet — A0, A1, A2 or A3 — along with a minimum body size in points and a headline size to match. Everything else about the design is yours; this only answers the question people get wrong.

The rule underneath it

Roughly 2.5 mm of cap height per metre of viewing distance. Two metres gives 5 mm, which lands near 20 pt.

Cap height, note. Not point size. Point size measures a notional body that takes in space above and below the letters, so two faces set at the same nominal size can differ by a fifth in how large the letters actually appear on the wall. The calculator converts for you, on an ordinary ratio.

The headline recommendation is three times the body size, which is a conventional and reliable ratio rather than a discovered law.

Density

Light means a handful of words: a title, two bullets, an image doing the work. Medium is a normal poster. Dense is a conference or research poster, with paragraphs and figures and a method section on it.

Denser content pushes you to a larger sheet because the type has to stay legible while there is more of it, not because the type gets bigger. That is worth saying plainly, since the usual instinct is to shrink the type to fit and it is precisely the wrong move — if it will not fit at legible size, the poster has too much on it.

Where the estimate stops working

It assumes ordinary eyesight, decent light, and a typeface of normal weight and width.

Go up a size for an older audience, for a dim corridor, for anything printed on gloss under downlighters, and for a condensed or light typeface. Go up two if the poster is a safety notice, where being read is not optional.

Printing it

Few home printers go past A4, so an A1 poster means a print shop — or tiling it across several sheets and taping them together, in which case add a millimetre or two of overlap and expect the seam to show.

Check the artwork resolution before you commit, with the resolution checker: an image that is sharp at A4 is a quarter of the resolution at A2 and often disappointing at A1. Large-format prints are viewed further back, which forgives a lot, but not everything.