Viewing Distance and Time

Viewing distance is one of the most important factors needed to determine the correct size of most electronic signs.
As a general rule: 1 inch of text is viewable up to 50 feet away1 or 25mm of text is viewable up to 15m away. The following diagram illustrates at what distance and character size that a stationary audience will recognize and understand the content of an electronic sign.

Viewing distance chart for electronic signs.

However, if the target audience is moving, then another factor, time, is required. Based on Grandwell's experience and research, an average of at least three to four seconds is required for a moving audience to adequately recognize and comprehend six to eight grouping of content on an electronic sign2. The following chart lists the maximum time an audience will have to view an electronic sign with specific characters size. For example, an audience will have three seconds or less to view electronic signs with four inches of text. If the electronic signs have too much content, than the reader will not have sufficient time to comprehend the entire content.

As a summary:
• 2 inch text works well in most foot traffic areas, such as for indoor applications.
• 4 to 6 inch text is ideal for 45mph or under traffic, such as outdoor church and school applications.
• 8 inch text  or larger works is suited for most outdoor applications where traffic is 60mph or slower.

Character Size Max. Viewing Distance Max. Viewing Time (seconds)3
inch mm foot meter 25mph / 40kph 35mph / 56kph 45mph / 72kph 55mph / 89kph 65mph / 104kph
2 51 100 31 2.7 1.9 1.5 1.2 1.0
4 102 200 61 5.5 3.9 3.0 2.5 2.1
5 127 250 76 6.8 4.9 3.8 3.1 2.6
6 152 300 91 8.2 5.8 4.5 3.7 3.1
8 203 400 122 10.9 7.8 6.1 5.0 4.2
9 229 450 137 12.3 8.8 6.8 5.6 4.7
10 254 500 152 13.6 9.7 7.6 6.2 5.2
12 305 600 183 16.4 11.7 9.1 7.4 6.3
16 406 800 244 21.8 15.6 12.1 9.9 8.4
20 508 1,000 305 27.3 19.5 15.2 12.4 10.5
24 610 1,200 366 32.7 23.4 18.2 14.9 12.6
36 914 1,800 549 49.1 35.1 27.3 22.3 18.9
48 1,200 2,400 732 65.5 46.8 36.4 29.8 25.2
60 1,542 3,000 914 81.8 58.4 45.5 37.2 31.5

Note:
1. LEDs emit light allowing the content to be visible further away than the same content on standard reflective surfaces.
2. Other factors, such as content size, traffic, distractions, weather, lighting conditions, etc. will affect the time required.
3. The values listed in the chart does not take into consideration the minimum required visibility distance (MRVD).
4. The information provided should not be taken as the definitive source on electronic sign visibility and viewing distance.

ISA, International Sign Association