Torx bit size chart
The point-to-point dimension is the width across the six lobes and it is what a caliper measures. It rises unevenly, so a T27 is not simply between a T25 and a T30 in a useful way; every size is its own fastener.
The screw match column is a rough guide, since a manufacturer can put any recess in any screw. Where it matters, measure the recess.
| Size | mm | inch | Typical fastener |
|---|---|---|---|
| T5 | 1.42 | 0.055 | Electronics, phones |
| T6 | 1.70 | 0.066 | Electronics |
| T7 | 1.99 | 0.078 | Small electronics |
| T8 | 2.31 | 0.090 | Small appliances |
| T9 | 2.50 | 0.098 | Small appliances |
| T10 | 2.74 | 0.107 | M3 screws, automotive trim |
| T15 | 3.27 | 0.128 | M3.5 screws, hard drives |
| T20 | 3.86 | 0.151 | M4 screws, automotive |
| T25 | 4.43 | 0.173 | M5 screws, decking, construction |
| T27 | 4.99 | 0.195 | M5 to M6 screws |
| T30 | 5.52 | 0.216 | M6 screws, automotive |
| T40 | 6.65 | 0.260 | M8 screws, brake calipers |
| T45 | 7.82 | 0.306 | M10 screws |
| T50 | 8.83 | 0.346 | M10 to M12 screws |
| T55 | 11.22 | 0.440 | M12 screws, heavy automotive |
| T60 | 13.25 | 0.519 | M14 screws |
| T70 | 15.51 | 0.610 | M16 screws |
Torx, Torx Plus and security Torx
Standard Torx has six rounded lobes and is designed so the driver bears on the flanks of the recess rather than the corners, which is why it takes far more torque than a Phillips or hex without camming out.
Torx Plus, marked IP, has squarer lobes and more contact area again. A standard Torx bit will fit a Torx Plus recess loosely and work at low torque; a Torx Plus bit will not enter a standard recess. Sizes are numbered the same, so a T25 and an IP25 are the same nominal size.
Security Torx, marked TR, has a pin in the centre of the recess so a plain bit cannot enter. The security bit has a matching hole. It is a deterrent rather than a lock, since TR bit sets are sold everywhere.
External Torx, marked E, is the male version used on bolt heads, and its numbers do not correspond to the T sizes at all: an E10 socket fits a head that is roughly the size a T50 bit would drive.
Getting the right size
A Torx bit that fits should drop in with no play and no forcing. If it wobbles it is a size small, and driving it that way rounds the recess. If it will not seat fully it is a size large or the recess is Torx Plus.
For a general set, T10 through T40 covers most of what a workshop meets. Add T8 and T9 for electronics, T45 through T55 for automotive and machinery, and a TR set if you service anything with tamper-resistant fixings.
