Torx Bit Sizes at a Glance
Torx sizes use T-number designations, not direct millimeter measurements. Common sizes include T10, T15, T20, T25, T30 and T40. The chart below lists the nominal internal hexalobular reference dimensions from T1 through T100 and provides inch conversions for quick comparison.
Important: T25 does not mean 25 mm, and the T-size does not identify the screw thread diameter or tightening torque.
Torx Bit Size Chart — T1 to T100
The table uses the nominal A and B dimensions for the internal hexalobular driving feature defined by ISO 10664:2014. The inch values are direct conversions from the nominal metric dimensions. Actual tools and recesses include tolerances and fit allowances, so use these dimensions as a reference rather than as a substitute for a product drawing or inspection gauge. Source [1]
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Scroll within this table to view additional columns or rows. The first column identifies each Torx size.
| T1 | 0.90 | 0.035 | 0.60 |
|---|---|---|---|
| T2 | 1.00 | 0.039 | 0.70 |
| T3 | 1.20 | 0.047 | 0.85 |
| T4 | 1.35 | 0.053 | 1.00 |
| T5 | 1.50 | 0.059 | 1.10 |
| T6 | 1.75 | 0.069 | 1.27 |
| T7 | 2.10 | 0.083 | 1.50 |
| T8 | 2.40 | 0.094 | 1.75 |
| T9 | 2.60 | 0.102 | 1.90 |
| T10 | 2.80 | 0.110 | 2.05 |
| T15 | 3.35 | 0.132 | 2.40 |
| T20 | 3.95 | 0.156 | 2.85 |
| T25 | 4.50 | 0.177 | 3.25 |
| T27 | 5.10 | 0.201 | 3.68 |
| T30 | 5.60 | 0.220 | 4.05 |
| T40 | 6.75 | 0.266 | 4.85 |
| T45 | 7.93 | 0.312 | 5.64 |
| T50 | 8.95 | 0.352 | 6.45 |
| T55 | 11.35 | 0.447 | 8.05 |
| T60 | 13.45 | 0.530 | 9.60 |
| T70 | 15.70 | 0.618 | 11.20 |
| T80 | 17.75 | 0.699 | 12.80 |
| T90 | 20.20 | 0.795 | 14.40 |
| T100 | 22.40 | 0.882 | 16.00 |
Dimension note: A and B describe nominal socket geometry in the standard; they are not universal measured driver-tip diameters. A properly fitting driver is intentionally smaller than the mating recess at corresponding features.
Torx Bit Size Chart | Turn2Engineering | Nominal reference dimensions; verify the actual fastener and tool before applying torque.
How Torx Dimensions Are Measured
How to Identify a Torx Bit Size
- Confirm the profile. Standard internal Torx uses a six-lobe recess. Do not identify a fastener from the word “star” alone.
- Check for a center pin. A six-lobe security recess with a center pin requires the matching size driver with a center hole.
- Look for the marked T-size. Driver bits are commonly marked T10, T15, T20, T25 and so on.
- Use dimensions only as a reference. Compare the nominal chart values when a marking is unavailable, but remember that driver and recess dimensions are not identical.
- Verify physical fit before torque. The correct bit should seat fully and have minimal rotational play. Stop if the bit is loose, shallow or forced.
Common Torx Bit Sizes
Torx usage varies by manufacturer and fastener design, but these ranges are commonly encountered:
These are broad application ranges, not a screw-size conversion. The specified drive size for the actual fastener controls.
Torx, Security Torx, Torx Plus and E-Torx
| Drive family | Identification | Tool requirement |
|---|---|---|
| Standard internal Torx | Six-lobe internal recess | Matching T-size driver |
| Security Torx | Six-lobe recess with center pin | Matching T-size security driver with center hole |
| Torx Plus | Broader, modified six-lobe profile | Matching Torx Plus tool; do not assume standard Torx is an equivalent substitute |
| External E-Torx | Male six-lobe fastener head | Matching E-size socket |
| Five-point security | Five lobes, sometimes with a center feature | Matching five-point security tool; not standard six-lobe Torx |
Correct Torx Fit: What to Check Before Applying Torque
If the bit is loose, shallow or will not seat, stop and check the specified size, lobe count, security pin, debris, coating buildup, tool wear and drive family. Do not hammer a mismatched driver into the recess.
Torx size does not specify tightening torque. Tightening torque depends on the fastener, material, lubrication, thread engagement, joint design and manufacturer specification.
Torx Size Is Not the Same as Screw or Socket-Drive Size
A T25 bit can be installed in a 1/4 in hex bit holder or carried by a 3/8 in square-drive bit socket and still be a T25 at the fastener. The T-number describes the six-lobe drive size; the holder or ratchet connection describes the tool interface; the screw thread has its own metric or inch designation.
Do not convert a T-number directly into a screw diameter. One Torx drive size may be used across more than one fastener size depending on the screw head and manufacturer.
Frequently Asked Questions About Torx Bit Sizes
What are the Torx sizes from smallest to largest?
The ISO 10664 internal hexalobular series covered here is T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T15, T20, T25, T27, T30, T40, T45, T50, T55, T60, T70, T80, T90 and T100.
What size is a T25 Torx?
The nominal ISO A dimension for a T25 internal hexalobular recess is 4.50 mm, or about 0.177 in. The actual driver is slightly smaller than the mating recess, so do not treat 4.50 mm as a universal measured bit-tip diameter.
What size is T30 Torx in millimeters?
The nominal ISO A dimension for T30 is 5.60 mm, with a nominal B dimension of 4.05 mm.
How do you measure a Torx bit size?
First identify the six-lobe drive family and check for a stamped T-size. If the marking is unavailable, a caliper measurement can be compared with nominal reference dimensions, but final identification should be confirmed by correct profile and physical fit.
Are star bits and Torx bits the same?
“Star bit” is commonly used as an informal name for six-lobe Torx-style tools, but not every star-shaped security drive is Torx. Count the lobes and check the actual drive family.
Can I use T25 instead of T27?
No. T25 and T27 are different drive sizes. An undersized bit may enter the recess but have excessive play and can damage the lobes under load.
Is T10 the same as E10?
No. T sizes identify internal-drive sizes while E sizes identify external Torx-style heads. Matching numbers do not make them equivalent dimensions or interchangeable tools.
What does security Torx mean?
For the common six-lobe tamper-resistant version, the screw recess has a center pin and the matching driver has a center hole. The drive size must still match.
Is Torx Plus the same as Torx?
No. Torx Plus uses a modified six-lobe geometry. Use the tool specified for the fastener rather than assuming a standard Torx driver is an equivalent substitute.
Does Torx size determine tightening torque?
No. The drive size alone does not determine tightening torque. Use the fastener or assembly manufacturer’s torque specification.
Can this chart be used to machine or inspect a Torx recess?
No. This page is a reference chart. ISO 10664 includes additional contour and gauging requirements, and ISO states that the standard is intended for inspection rather than as a manufacturing standard. Use the applicable controlled standard and product drawing when geometry or conformity controls.
Sources and Data Basis
The page distinguishes nominal internal-recess dimensions from actual tool-tip dimensions and from external E-Torx sizing. Metric nominal A/B values follow the current ISO 10664:2014 internal hexalobular reference; inch values shown in the main chart are calculated conversions using 25.4 mm per inch.
- ISO 10664:2014 — Hexalobular internal driving feature for bolts and screws. ISO states that the standard specifies shape, basic dimensions and gauging for the internal hexalobular feature and that the 2014 edition was reviewed and confirmed in 2024.
- TORX Products — drive size reference. Used as a practical cross-check that actual driver point-to-point dimensions are slightly smaller than corresponding nominal internal-recess reference values.
- Wiha — Torx tool families. Used to cross-check practical separation of standard, security and Torx Plus tool families.