It depends on the size and font, so please refer to the following table.
Shape | Size | Standard character size |
Square | 5" × 5" (130 × 130 mm) | 5/16" - 3/8" (8-10mm) |
Rectangle | 7" × 2" (175 × 55 mm) | 1/4" - 5/16" (6-8mm) |
Square Bar | 7" × 1" × 1" (168 × 25 × 25 mm) | 3/16"- 1/4" (5-6mm) |
The letter sizes for the Big and Small designs are as follows:
Big: 5/16" - 3/8" (8-10mm)
Small: 3/16" (4-5mm)