ADA braille dot dimensions, spacing and position.
Contracted braille is not a visual font substitution. Dot shape, cell geometry, capitalization and placement are controlled manufacturing dimensions.
Federal braille geometry
| Measurement | Permitted range |
|---|---|
| Dot base diameter | 0.059–0.063 inch |
| Dots within the same cell, center to center | 0.090–0.100 inch |
| Corresponding dots in adjacent cells, center to center | 0.241–0.300 inch |
| Dot height | 0.025–0.037 inch |
| Corresponding dots in a cell directly below, center to center | 0.395–0.400 inch |
Contracted braille and capitalization
Section 703.3 requires contracted braille, commonly called Grade 2. Braille dots must have a domed or rounded shape. The uppercase indicator is limited to the first word of sentences, proper nouns and names, individual alphabet letters, initials and acronyms.
Position below the corresponding text
Braille is positioned below the corresponding text. For a multi-line message, it is placed below the entire text block. Braille must be separated at least 3/8 inch from other tactile characters and at least 3/8 inch from raised borders and decorative elements.
The elevator-control exception uses a different minimum separation and location rule; it should not be generalized to ordinary room-identification signs.
Primary reference: 2010 ADA Standards, Section 703.3. State/local requirements and project documents may add conditions.