Start with where people will be
- Pedestrians on the same side – a few metres away, walking slowly.
- People across the street or mall walkway – further away, with more distractions.
- Drivers – often tens of metres away, moving, with only a few seconds to read.
- Visitors inside a building – close up, looking for a specific room or desk.
Stand where your customers will be, or look at the spot on a map, and estimate the distance. That distance drives everything else.
Letter height rules of thumb
There is no single official formula, but sign makers use rough rules of thumb. A commonly quoted one is roughly 25mm of letter height for every 3m of viewing distance for comfortable, quick reading. Many people can read smaller text if they stop and look, but signs are rarely read that way.
Treat any rule as a starting point. Font, contrast, lighting and how busy the sign is all change readability. The most reliable test is a mock-up at full size.
Speed changes everything
Drivers only see a sign for a short time, so roadside signs, pylons and billboards need fewer words and larger letters than shopfronts read by pedestrians. As a guide, a driver can take in a name, a logo and perhaps one short line. Long lists of services on a roadside board will not be read. See pylon signs and billboard printing.
Other things that affect readability
- Contrast – dark on light or light on dark. Similar colours reduce readable distance a lot.
- Font – simple, bold fonts read further than thin, decorative or script fonts.
- Spacing – letters and lines need breathing room; cramming reduces legibility.
- Capitals vs lower case – mixed case is often easier to read at a glance than all capitals.
- Lighting – at night, only lit signs or well-lit areas work. See illuminated vs non-illuminated signs.
- Clutter – the more items on a sign, the smaller each one becomes.
Test before you order
- Print your key word at the planned size on paper and tape it up where the sign will go.
- Walk or drive past at normal speed and see if it is readable.
- Ask someone unfamiliar with the business to read it.
- Mark out the full sign size with masking tape to judge proportion.
Our sign design service plans text size around viewing distance, and our team can advise when you request a quote. Remember that larger external signs may need approval; see signage approvals.
