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The quickest way to settle sign text size is to work backwards from the reader. Measure how far off they’ll be, then give each 3 m of distance 25 mm of capital height. That’s a long-standing sign-trade rule of thumb, and half of it is the floor for anything at all. So a reader 15 m away needs capitals around 125 mm tall, and one 3 m away needs around 25 mm. Safety signs are the exception, because they’re sized by the whole sign rather than the letters. Tables and examples follow.
Step one: find your reader #
Before touching the design, go and stand in the reader’s shoes. That might be the far kerb, the entrance barrier of a car park, or the last row of chairs. Pace out or measure the distance to where the sign will hang. That one number drives everything else.
Be honest about it. People rarely walk right up to a sign. They read it on the move, from wherever they happen to be, or not at all.
Sign text size by distance #
The rule works out at roughly 8.3 mm of capital height per metre. Two columns here: one for things people must spot while passing, one for detail they’ll stop and read.
| Reader’s distance | Headline capitals (to be noticed) | Minimum for detail (half) |
|---|---|---|
| 2 m | 17 mm | 8 mm |
| 4 m | 33 mm | 17 mm |
| 6 m | 50 mm | 25 mm |
| 8 m | 67 mm | 33 mm |
| 12 m | 100 mm | 50 mm |
| 25 m | 208 mm | 104 mm |
| 40 m | 333 mm | 167 mm |
The headline column is for your name, your number and anything that has to register in a glance. The detail column suits things people pause for, like a list of hours on a shop door. It’s the same distance rule our artwork guidelines use.
From millimetres to font size #
Design programs size text in points, and the point size of a font is taller than its capitals. One point measures roughly a third of a millimetre (0.353 mm). With a chunky sans serif, a capital letter usually stands at about seven tenths of the point size. Combine the two and you get a rule you can do in your head: points ≈ capital height in mm × 4, at full size.
- 17 mm capitals: about 68 pt.
- 50 mm capitals: about 200 pt.
- 100 mm capitals: about 400 pt.
Fonts vary, so test yours. Zoom to 100% and measure a capital H with a ruler against the screen. Better still, print a single letter at full size, tape it to a wall and back off to your measured distance. Working at 1:10? Take a tenth of the point size; our guide to 1:10 scale artwork covers the rest.
Safety signs follow a different rule #
On a safety sign, most of the message comes from the pictogram, the colour and the shape, so it’s the overall dimensions that matter. Our safety sign colours and shapes guide follows the distance-factor approach from ISO 3864-1: every 25 mm on the shorter edge buys you roughly a metre of reading distance. In practice:
| Sign | Shorter edge | Readable up to roughly |
|---|---|---|
| A4 | 210 mm | 8 m |
| A3 | 297 mm | 12 m |
| A2 | 420 mm | 17 m |
| A1 | 594 mm | 24 m |
Employers’ obligations around safety signage are set by the Health and Safety (Safety Signs and Signals) Regulations 1996, with the risk assessment deciding where each sign goes. Dim spaces, or people moving quickly past, are a cue to size up.
Three worked examples of sign text size #
A pavement A-board
Put an A1 poster, 594 mm wide, in an A-frame pavement sign and most readers are pedestrians somewhere between 3 and 10 m away. Plan for the far end: capitals near 83 mm. You’ll squeeze in somewhere between eight and ten of those per line, which means a headline of a couple of short words, such as “Open today”. Prices or offers lower down can come in at 40 to 50 mm, since people have slowed by the time they get there.
A banner on railings by a road
Hang a 6 ft × 3 ft banner (1829 × 914 mm) where drivers see it and you’re often designing for 15 m plus, so the lead line wants capitals near 125 mm. Take the 50 mm the hems and eyelets need off each edge of the 914 mm height and there’s space for that headline, a 60 to 80 mm line of detail and a number, with gaps. Anything more squeezes every line smaller. Our online designer warns you on this banner size when capitals drop below about 40 mm, since they’ll struggle at 10 m.
An A2 sign at a site entrance
Fix an A2 Correx board (420 × 594 mm) at a site gate and drivers pulling in could be 10 m off. That means capitals of about 83 mm, and only five or six will fit side by side on a 420 mm portrait board. “Deliveries” fits. A sentence won’t. Add a safety symbol and, by the whole-sign rule above, that A2 is readable to around 17 m, so the symbol registers well before the text.
It isn’t only about height #
Two signs with identical letter heights can read very differently. Watch these:
- Contrast. Pale letters on a dark ground, or the reverse. Yellow with black, or dark blue with white, read from a long way off. Grey on white and red on green struggle.
- Typeface. Simple, heavy, no frills. Handwriting styles, hairline weights and squashed fonts must be much bigger to match.
- Capitals or not. Short headlines look punchy in capitals. Longer lines are easier in upper and lower case; just size by the capital height regardless.
- Speed. Anyone driving has a moment, not a minute. Cut words instead of shrinking them.
- Breathing room. Leave space round each line. Crammed text blurs into one grey block.
For pinning down the space and distance before you design, see measuring up for a banner, and for tall displays, roller banner design. Still unsure about your sign text size? Send the sign size, the wording and the distance through the contact form and we’ll tell you whether it’ll read.