Visibility of LED Digital Clock Displays

Factors to Consider: Size and Color

Masterclock digital clock displays range in digit size from 0.6 inches (1.5 cm) to 8 inches (20 cm). Our digital clocks use diffused LEDs to create light. Seven LED segments shape the numbers. Ten define the letters. Most sizes are available in your choice of red, amber, green, blue or white.
 
In typical locations most people consider red to be the most visible color. In dimmer light amber and green tend to be more pleasing and less distracting. At greater distances most people consider blue to be less visible.
 
Eyesight imperfections and adverse lighting conditions tend to diminish the visibility of the digits. Factors associated with the specific installation must also be considered, such as the ceiling height, window vicinity and indoor lighting.

How to Decide Which Size is Best

As a guide you should increase the digit size one inch for every 50 feet of viewing distance. Therefore, a 0.6-inch (1.5 cm) display would be visible no further than thirty feet (9 m) away. A 2.3-inch (5.8 cm) display would increase the visibility distance to 100 feet (30 m).
 
At these maximum distances please consider that a person would have to stop and concentrate to read each display. For the quick and casual observer the above estimates should be cut in half. Thus a casual observer at 50 feet (15 m) would need a 2.3-inch (5.8 cm) display. At 100 feet (30 m), a 4-inch (10 cm) display would be better.
 
If you are concerned about the size and color of your display, our experience may help. We look forward to providing you a digital clock that everyone can read and enjoy.

Digit Size Maximum Viewing Distance Typical Viewing Distance
0.6 in
(1.5 cm)
30 ft
(9 m)
15 ft
(5 m)
1 in
(2.5 cm)
50 ft
(15 m)
30 ft
(10 m)
2.3 in
(5.8 cm)
100 ft
(30 m)
50 ft
(15 m)
4 in
(10 cm)
200 ft
(60 m)
100 ft
(30 m)
7 in
(18 cm)
350 ft
(100 m)
175 ft
(50 m)