Common Torx Sizes and How to Match the Bit
Quick answer: Common Torx drive sizes include T10, T15, T20, T25, T30 and T40, but the correct size depends on the screw—not the application alone. Smaller electronics and larger construction fasteners use sizes outside this range.
Key points
- The T number identifies the driver size, not the screw diameter.
- A bit should fill the recess with minimal play.
- Torx and security Torx are different; security versions have a center pin and need a compatible bit.
How to choose or use it
Clean debris from the recess, test the bit by hand and keep it straight while driving. Stop if the bit rocks or bottoms incorrectly. Using a near-size bit can damage both the recess and tool.
Installation and safety checklist
- Confirm the receiving material, hole preparation and mating thread.
- Verify diameter, pitch, length, head, drive, material and finish.
- Use a well-fitting tool, keep it aligned and tighten only to the required seating or specified torque.
- For structural, overhead or safety-critical joints, follow the approved design, code and manufacturer data.