Torx Bit Sizes: T7, T15, T20, T30, T40 Guide
By Drill Hog® | Published: 2026-10-20
Category: Buying Guides
Learn which Torx bit size you need for common fasteners. This guide covers T7 through T40 sizes and helps you choose the right set for your projects.
Quick answer
Match the Torx bit size to the fastener's star drive: T7 for tiny electronics, T15 for small appliances, T20 for automotive interior trim, T30 for brake calipers and T40 for heavy-duty bolts.
Why Torx bits resist cam-out better than Phillips
The six-point star shape of a Torx bit distributes torque across a wider contact area than a Phillips cross. This reduces the chance of the bit slipping out (cam-out), which can strip the fastener head or damage the workpiece. For high-torque applications like automotive or construction, Torx is a reliable upgrade.
The trade-off: you need the exact size
Unlike Phillips or slotted drives that tolerate slight size mismatches, Torx bits must match the fastener exactly. A T15 bit will not fit a T20 screw, and forcing it can round off the drive. This makes a full set of sizes essential if you work with multiple fastener types.
How to choose the right Torx bit size
- T7 (0.91 mm tip): Use for tiny screws in electronics, eyeglasses, and small appliances. Not for structural or high-torque work.
- T15 (1.60 mm tip): Common in small power tools, laptop hinges, and some automotive interior panels. A good all-around small size.
- T20 (2.08 mm tip): The most popular Torx size for automotive trim, door panels, and dashboards. Also found on many bicycle components. If you only buy one size, T20 covers the widest range of common fasteners.
- T30 (2.60 mm tip): Standard for brake calipers, seat belt anchors, and suspension components. Requires a bit with impact rating for high torque.
- T40 (3.15 mm tip): Used on large bolts in truck hitches, engine mounts, and heavy equipment. Needs a strong bit to avoid twisting. A T40 bit should always be impact-rated to handle the torque these fasteners demand.
Torx bit options from Drill Hog
- T-15 Torx Bit Hi-Molybdenum Super M7+ Drill Hog® 10 Pack: Drill Hog T-15 Torx Bit Hi-Molybdenum Super M7+ 10 Pack is impact rated and made from Hi-Molybdenum Super M7+ with a melting point of 4,753°F. The high-molybdenum alloy handles sustained impact driver use without softening or breaking, making it a durable choice for automotive and construction fasteners.
T-15 Torx Bit Hi-Molybdenum Super M7+ Drill Hog® 10 Pack - T-40 Torx Bit Hi-Molybdenum Super M7+ Drill Hog® 10 Pack: Drill Hog T-40 Torx Bit Hi-Molybdenum Super M7+ 10 Pack is impact rated and made from Hi-Molybdenum Super M7+ with a melting point of 4,753°F. T40 is the largest common Torx size for heavy-duty bolts; this bit's heat resistance keeps it reliable under high torque in metal framing or suspension work.
T-40 Torx Bit Hi-Molybdenum Super M7+ Drill Hog® 10 Pack
Which Torx bit set fits your work?
Best for
- DIYers and mechanics who work on cars, bikes, or appliances and need a range of sizes
- Anyone upgrading from Phillips to reduce cam-out on high-torque fasteners
Not for
- Projects that use only one fastener size (buy a single-size pack instead of a set)
- Fasteners with security Torx (pin-in-center) which require a special hollow bit
