A practical calculation for the letter height that determines how far away your sign can be read, plus other factors affecting legibility such as typeface, colour and lighting.
A big sign doesn't automatically mean a readable one. The most important measure of legibility is letter height. If the letters are too small, the sign looks like a blur from a distance; if they are bigger than necessary, it can cause problems with both your budget and municipal rules.
A practical calculation
There is a practical rule commonly used in the sign industry: every 2.5 cm of letter height can be read comfortably from about 3 metres. So, roughly:
- 10 cm letters: comfortably readable from about 12 metres.
- 20 cm letters: comfortably readable from about 24 metres.
- 30 cm letters: comfortably readable from about 36 metres.
- 50 cm letters: comfortably readable from about 60 metres.
These values are approximate figures for good conditions. Typeface, colour and lighting can increase or reduce legibility.
How do you determine viewing distance?
Ask yourself: where should my customers see my sign from? For a pedestrian on the opposite pavement, 15-20 metres may be enough. For a driver passing along the street, the distance is much greater, and the driver only has a few seconds to notice and read the sign. Signs aimed at vehicle traffic need larger letters.
Other factors affecting legibility
- Typeface: simple, bold typefaces read better from a distance. Thin, script or highly ornate typefaces shorten the viewing distance.
- Contrast: the greater the difference between background and text colour, the better the legibility. Light text on a dark background or dark text on a light background gives the best result.
- Letter spacing: if the letters are too close together, they blur into each other from a distance.
- Lighting: for signs that need to be seen at night, illuminated letters can be read from much further away than non-illuminated letters of the same size.
- Text length: the fewer words on the sign, the faster it is read. The brand name plus a one- or two-word business description is usually enough.
How do we measure during the site survey?
During the site survey, we look at the facade from the points the sign needs to be seen from, measure the distance and set the letter height according to the facade size. We then present the sign's actual look on the building in a 3D design for your approval. That way, you can be sure the dimensions are right before the sign is produced.
