What letter size should I use on my sign?

The following chart is a standard guideline used by most sign professionals and is only accurate if your sign has adequate contrast (like black in white and NOT something like gray on white):

Letter Height
(in Inches)

Maximum Readable
Distance

Distance for
Maximum
Impact
2"
50'
20'
3"
100'
30'
4"
150'
40'
6"
200'
60'
8"
350'
80'
9"
400'
90'
10"
450'
100'
12"
525'
120'