The chart below shows the maximum reading distance for your sign to make the best impact. A good rule of thumb is every 1 inch of letter height provided 10 feet of readability. For example, 3" tall letters make the best impact within 30'; however, they can still be seen and read from up to 100' away.
Contrasting colors will increase the sign visibility as well. For example, red, black and dark brown are strong colors and contrasting them with white or gold will work well.