Torx Screw Sizes Explained — T10, T20, T25, T30 and More

Torx Screw Sizes Explained — Which T Size for Which Screw?

Torx screws use a six-pointed star recess that provides excellent torque transfer with virtually no cam-out. Originally developed for automotive assembly, Torx has become increasingly popular in UK construction, particularly for decking screws and high-performance wood screws. This guide covers every common Torx size, what each is used for, and how to choose the right bit.

Why Torx Is Replacing Pozidriv in Some Applications

The six-pointed star shape of a Torx recess distributes torque more evenly across the bit than a cruciform (PZ/PH) design. This means less cam-out, less wear on the bit, and the ability to apply higher torque without the bit slipping. For high-torque applications like decking, Torx has largely replaced Pozidriv as the screw head of choice. Premium screw brands like Spax, HECO, and TIMco use Torx across most of their construction ranges.

Complete Torx Size Chart

Two columns, two different things. The recess column is the “A” across-points dimension defined by ISO 10664, the standard governing the hexalobular socket in the screw head. The driver column is the approximate across-points size of the bit, which must sit slightly under the recess to enter it. The screw-gauge column is an editorial guide for UK woodscrews — ISO 10664 does not map socket sizes to screw diameters and refers users to the relevant product standards, so check the screw manufacturer’s own recommendation for structural work.

Torx vs Security Torx (Tamper-Proof)

Security Torx (sometimes written as TT, TR, or Torx Pin) screws have a small pin in the centre of the star recess. This pin prevents a standard Torx bit from seating. You need a security Torx bit with a matching hole to drive these screws. They’re used in places where you don’t want the public removing fasteners — playground equipment, public bench fixings, anti-theft fixings, and security panels.

If you work on outdoor or public installations, it’s worth having a set of security Torx bits. They’re inexpensive and commonly sold as TR10–TR40 (also written T10H–T40H). Note that this is narrower than the standard Torx range charted above, which starts at T6 — and that the H and TR suffixes are vendor conventions rather than ISO designations.

Which Torx Sizes Do I Actually Need?

For most UK DIY and trade work, you’ll use T20 and T25 the most. T25 is the standard for decking screws, Spax construction screws, and most modern timber fixings. T20 covers lighter-duty Torx screws for interior work and furniture. Beyond that, T10 and T15 are useful for electronics and small machine screws, while T30 and T40 are specialist sizes for heavy structural work.

If you use an impact driver for decking or construction, buy T25 impact bits in bulk — you’ll use them constantly. See our impact driver bits guide for impact-rated Torx bit recommendations.

Recommended Torx Bit Sets

Wera 867/1 Impaktor Torx Bit Set

Wera’s Impaktor Torx bits feature diamond-coated tips that grip the screw head with exceptional precision. Available in sets covering T10–T40, these are impact-rated and compatible with any 1/4″ hex driver. The quality is a clear step above budget alternatives — the tips stay sharp significantly longer under heavy use.

Makita Impact Gold Torx Bit Set

Makita’s Impact Gold Torx bits use Xtreme Torsion technology and come in T10–T40 sizes. These are a solid mid-range option that works well in Makita impact drivers (and any other brand). The gold coating provides corrosion resistance and makes them easy to identify in a mixed bit collection.

For a complete overview of every screw type and the matching bit, see our complete screw-to-bit reference table.