Poster design rules that work from across a room
A poster is read in three seconds from three metres. Nine rules that follow from that, with the numbers: how big the type must be, how many sizes to use, where the details go, and the two tests to run before you export.
Beginner6 min readUpdated 27 September 2026Editor · Guides, Character panel
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1. One message
Decide the one thing a passer-by should take away, and make that the headline. Everything else is detail. A poster that also explains the organisation, lists six sponsors at the same size and adds a slogan has three headlines and no message. If the client insists on more, the answer is two posters.
2. Size type for the distance
A signage rule of thumb: for comfortable reading, capital letters need about 10 mm of height for every 3 m between reader and poster, and to be noticed rather than merely readable, double it. A poster on a corridor wall is read from 2 to 3 m; one across a street from 10 m or more.
| Read from | Smallest details (cap height) | Headline (cap height) | On an A3 at 300 dpi |
|---|---|---|---|
| 1 m (notice board, up close) | 4 mm | 15 mm and up | details 47 px, headline 180 px+ |
| 3 m (corridor, shop window) | 10 mm | 30 mm and up | details 118 px, headline 350 px+ |
| 10 m (across a street) | 35 mm | 100 mm and up | A3 is too small; use A1 or larger |
Cap height is roughly 70 per cent of the point size for most fonts, so a 10 mm capital is about a 14 mm (40 pt) setting. In the Editor, set sizes in the Character panel in pixels: at 300 dpi, 1 mm is 11.8 px. The Properties slider stops at 600 px; the Character panel does not.
3. Three sizes, clearly different
Headline, facts, small print. Each level at least 1.5 times the next, and the headline usually three times the facts. Four sizes is the maximum; more and the hierarchy dissolves. One type family with a range of weights is always safe; a display face for the headline over a plain sans for the facts is the classic poster pairing. Pick sizes from a scale rather than by eye:
4. One focal point
One element wins: the headline, or the image, never both. Make it win by a wide margin, two to three times the size of the next thing, or the only thing in colour, or the only thing with space around it. A poster with two equal things has a tie, and the reader walks past a tie.
5. Margins and a grid
Keep everything at least 5 per cent of the short side away from the edge (15 mm on A3, 25 mm on 18 × 24 in). Printers trim with a small tolerance, frames cover edges, and a margin makes the design look placed. Inside the margin, align to two or three edges, not seven. The Editor's View, Guides, New guide layout… has a Safe margins preset; set the margin in pixels and snap to it.
6. Two colours and a neutral
A background, a type colour and one accent is a complete poster palette. Contrast between the type and what is behind it matters more than the colours themselves: dark on light or light on dark, at 4.5:1 or better, because posters are read in bad light. Bright saturated colours print duller than they look on screen, so put the neon in the accent, not the background. Colour that works has the system.
7. Details in reading order
After the headline the eye wants: what it is, when, where, how much and how to get in. Put them in that order, top to bottom or in one block, in the second size, aligned to one edge. Logos go at the bottom in a row, aligned along their base, each no taller than the small print is wide. A QR code is a detail: 25 mm minimum for a 1 m scan, with quiet space around it.
8. The two tests
- Squint. Blur your eyes (or add a Black and white adjustment layer and step back). What still stands out is the real focal point. If it is the sponsor strip, fix the tone.
- Phone size. Zoom out until the poster is the size of your phone screen. If you can still read the headline and the date, it works from across a street. If not, the type is too small or the contrast too low.
- Then 100 per cent (Ctrl+1) to check the photo and the smallest type at print scale, because the phone test hides softness.
9. The right resolution
300 dpi for A3 and smaller, 150 dpi for A2 and larger, and the photo's own pixels checked at final size. What dpi a poster should be has the table; How to prepare a poster for print has the export.
Common mistakes
| Mistake | What it looks like | Fix |
|---|---|---|
| Everything the same size | A wall of text; nothing to read first | Three sizes, headline 3× the facts |
| Centred everything | Ragged edges everywhere, no line to follow | Align to one left edge, or centre only the headline |
| Type over a busy photo | Half the letters vanish | Tone the photo down under the type, or put the type on a flat band |
| Too many fonts | Looks like a ransom note | One family, or two with different jobs |
| Small text at the edge | Cut off or hidden by the frame | Safe margin, and nothing important in the bottom 5 per cent |
| Neon background | Prints muddy | Neutral or dark background, neon as accent |
- One message; the headline says it.
- Headline capitals at least 30 mm for a 3 m read; details at least 10 mm.
- Three type sizes, each at least 1.5× the next.
- One focal point; the squint test agrees.
- Safe margin on all sides; two or three alignment edges.
- Two colours and a neutral; type contrast 4.5:1 or better.
- What, when, where, price, how to get in, in that order.
- Passes the phone-size test; checked at 100 per cent.
- 300 dpi at A3 and below, 150 above; photo pixels checked at final size.
How Voidcanvas handles this
Print presets at 300 dpi, a Safe margins guide layout that snaps, the Character panel for headline sizes beyond the slider, adjustment layers to tone a photo down under type, Ctrl+1 for the print-scale check and a one-page PDF at 300 dpi. The event poster workflow applies all nine rules to one real job.
How big should text be on a poster?
For a 3 m read, capitals at least 10 mm tall for details and 30 mm or more for the headline; double those to be noticed rather than merely legible. At 300 dpi, 10 mm is about 118 px.
How many fonts should a poster use?
One family with a range of weights, or two with different jobs (a display face for the headline, a plain face for the facts). Never three.
What size should a poster be?
A3 for notice boards and shop windows read up close, A2 or A1 for walls and read from a few metres, A0 or larger across a street. The bigger the poster, the further away it is read and the lower the dpi it needs.