ADA character height calculator
Enter the height of the character baseline above the floor and the horizontal viewing distance to the nearest obstruction. The minimum height of the uppercase I comes from Table 703.5.5, rounded up to the next 1/16 inch.
How it works
| Baseline height | Threshold distance | Minimum below threshold | Beyond threshold |
|---|---|---|---|
| 40 in to 70 in | 72 in (6 ft) | 5/8 in | + 1/8 in per ft over 6 ft |
| over 70 in to 120 in | 180 in (15 ft) | 2 in | + 1/8 in per ft over 15 ft |
| over 120 in | 21 ft | 3 in | + 1/8 in per ft over 21 ft |
The calculator applies the 1/8 inch per foot in proportion to the distance past the threshold, then rounds the result up to the next 1/16 inch, so a partial foot never leaves you under the minimum. Visual characters below 40 inches do not comply at any size (703.5.6). The result is the height of the uppercase I in the font you use; check the font's proportions separately on the fonts page.
Viewing distance is measured horizontally from the characters to the nearest obstruction that stops a reader going closer: a counter, a railing, a planter, the edge of a mezzanine. If nothing stops them, the reader can walk up to the sign and the base minimum for the height band applies.
These are minimums for accessibility, not design targets. Overhead wayfinding usually looks right at well above the minimum, and the minimum does not account for poor lighting or busy backgrounds. Size from the calculator, then check a full-size print from the actual viewing position.
Questions
How do I calculate ADA letter height?
Find the row of Table 703.5.5 for the height of the character baseline above the floor, then the horizontal viewing distance to the nearest obstruction. Below the threshold distance the minimum is 5/8, 2 or 3 inches; beyond it, add 1/8 inch for each foot past the threshold.
Does the calculator apply to raised characters?
No. Raised (tactile) characters are always 5/8 to 2 inches, or 1/2 inch minimum where separate visual characters are provided. The table and this calculator are for visual characters only.
What if there is nothing stopping people walking up to the sign?
Then the viewing distance is short, since a reader can approach the sign, and the base minimum for the height band applies: 5/8 inch at 40 to 70 inches, 2 inches up to 120 inches, 3 inches above that.
Last checked against the source text 2026-09-25. Section numbers refer to the 2010 ADA Standards unless marked otherwise.