How to choose sign letter height
The most common sign-industry rule is one inch of letter height for every 10 feet of viewing distance for comfortable, at-a-glance reading. A 4-inch letter reads easily at 40 feet. Letters stay technically legible much farther — roughly 25–30 feet per inch with bold, high-contrast lettering — but people have to stop and concentrate to read them.
Signs for drivers
For roadside signs, distance isn't fixed — the driver is moving. The calculator estimates how far away a driver needs to start reading: about 4 seconds to notice and react, plus reading time of roughly 2.5 words per second, multiplied by speed. At 35 mph a 5-word sign needs to be readable from about 310 feet, which means letters of roughly 12–15 inches. That's why short messages work best on the road.
What affects readability
- Contrast: black on white, white on red, yellow on black and white on blue read best. Low-contrast pairs can cut readable distance by a third.
- Font: bold, simple sans-serif fonts read farthest. Thin, condensed and script fonts need larger letters.
- Spacing: crowded letters blur together at a distance. Leave margin around the text — at least one letter-height on each side.
- Lighting: unlit signs at night lose most of their range.
Estimating sign size from your text
Enter your longest line of text and the calculator estimates the overall sign or banner size using an average bold-font letter width of about 0.65× the letter height, plus margins, and suggests the nearest standard banner size that fits.
Results are estimates based on common sign-industry guidelines. Local sign codes may limit sign size — check with your city before ordering.