Size

Assuming the sign can be seen from the distance listed in Table 4, the next step is to figure out how large the letters on your sign need to be so that your message can be read.

 

Experts recommend designing signs with letters a minimum of one-inch tall for every twenty-five feet of distance.  This makes them readable for all legal drivers.  In our example, then, the smallest letters on a sign would be 16.4 inches in height if it were to be read from 410 feet away (assuming 30 mph traffic moving in two lanes in each direction).  Note that if your sign is using fancy lettering that is more difficult to read, the minimum letter size must be increased significantly.

 

To figure out the smallest possible size your sign can be and still be readable, figure each letter in the message will take up one square.  In our example, that would be 16.4 square inches, or 1.37 square feet, for each letter.  That allows for space between lines and words.  If the sign read, Lydia’s Beauty Supply, its 18 letters would need a minimum of 25 square feet just for the words.  For optimum clarity, an additional 40% of empty or white space would be needed, for a total of 35 square feet.  That would be the absolute minimum size for a perpendicularly mounted sign with no graphics and very plain, easy to read lettering.

 

Most businesses are not going to be well served by a small, plain sign with no graphics.  The lettering style, the ability of graphics and logos to be easily recognized, whether or not the words on the sign are familiar and easy to read, the lighting methods used, and even the colors used all impact people’s ability to see and read a sign.