Torx Bit Size Chart

T1–T100 Torx bit sizes in mm and inches. Find common star-bit widths instantly, including T25 and T30.

Find Your Torx Bit Size

T25 bit tip: 4.43 mm (0.174 in) point-to-point. The nominal screw recess is 4.50 mm. Why different?

Common Torx sizes bit-tip widths

T102.74 mm T153.27 mm T203.86 mm T254.43 mm T305.52 mm T406.65 mm

Approximate tip widths, not screw thread sizes. See all 24 sizes →

Important: T25 does not mean 25 mm. T-size identifies a six-lobe drive; torque and screw-thread size are specified separately. Data basis.

Torx Bit Size Chart (T1–T100)

Find the full 24-size Torx chart below. Bit tip = approximate point-to-point tool width; ISO recess A = nominal width inside the screw. Both are provided to prevent a misleading conversion. See the measurement diagram.

On small screens, swipe horizontally to view the ISO recess column.

Approximate six-lobe Torx driver point-to-point widths compared with ISO 10664:2014 nominal internal recess A dimensions.

T1	0.81	0.032	0.90
T2	0.93	0.037	1.00
T3	1.10	0.043	1.20
T4	1.28	0.050	1.35
T5	1.42	0.056	1.50
T6	1.70	0.067	1.75
T7	1.99	0.078	2.10
T8	2.31	0.091	2.40
T9	2.50	0.098	2.60
T10	2.74	0.108	2.80
T15	3.27	0.129	3.35
T20	3.86	0.152	3.95
T25	4.43	0.174	4.50
T27	4.99	0.196	5.10
T30	5.52	0.217	5.60
T40	6.65	0.262	6.75
T45	7.82	0.308	7.93
T50	8.83	0.348	8.95
T55	11.22	0.442	11.35
T60	13.25	0.522	13.45
T70	15.51	0.611	15.70
T80	17.54	0.691	17.75
T90	19.92	0.784	20.20
T100	22.13	0.871	22.40

What is the difference? Driver-tip figures are approximate published tool dimensions. ISO 10664 A is the nominal recess reference. Bit-tip size varies with manufacturing tolerances, wear, and supplier; it cannot replace a fit check.

Inch values are calculated from the listed approximate millimeters using 25.4 mm/in, rounded to three decimal places.

Torx Bit Size Chart | Turn2Engineering | Driver-tip dimensions are approximate. ISO A/B values are nominal recess dimensions.

Torx vs. Security Torx vs. Torx Plus vs. E-Torx

First identify the drive shape, then pick the size. A same-number T bit and E socket are not equivalent, and a Torx Plus fastener calls for an appropriate Plus tool.

Identification schematics only; lobes are simplified, not dimensioned manufacturing contours.

Standard Torx (T)Six-lobe recess with no pin. Match the numbered T bit.

Security Torx (TR / tamper-resistant)Six-lobe recess with a center post. Use a security Torx bit of the matching T-size with a hole.

Torx Plus (IP)Broader, modified lobes. Use the specified IP bit, especially for high-torque work.

External E-Torx (E)Raised six-lobe bolt head. Requires a matching E-series socket rather than a T bit.

Five-lobe security fasteners are another drive family; a six-lobe Torx bit is not a proper replacement.

How to Measure or Identify an Unknown Torx Bit

Count six lobes. Check if the fastener is standard internal Torx, center-pin security Torx, Plus or E-Torx.
Check the bit marking. A stamped T20, T25 or T30 is more reliable than estimating from the screw head diameter.
Measure across opposite lobe tips. If unmarked, take a point-to-point measurement of an undamaged driver with calipers and use the lookup above to find likely sizes.
Test the fit by hand. The correct tool should seat fully without forcing and should not rock excessively. If it is loose or wedges shallowly, check the next size and drive family.
Use the prescribed torque. The T-size alone does not establish a safe installation or removal torque.

Example: If your Torx bit measures about 4.4 mm across the tips, T25 is a reasonable candidate (listed around 4.43 mm). A T25 screw recess has nominal ISO A of 4.50 mm, so measuring the bit and measuring the recess are different checks.

Engineering Reference: ISO Torx Recess Dimensions A and B

ISO 10664:2014 defines a hexalobular internal driving feature for screws. In the recess cross-section, A is the larger nominal reference width across opposite lobe tips and B is the smaller width across the valleys. These are not actual driver-tip specifications.

Conceptual A/B reference only. Inspection uses the complete standard and appropriate gauges.

T25 example

Approx. bit-tip width: 4.43 mm
Nominal recess A: 4.50 mm
Nominal recess B: 3.25 mm

Use ISO 10664 and controlled product drawings for inspection, not this simplified schematic.

Show the full ISO nominal A and B chart (T1–T100)

ISO 10664:2014 nominal internal hexalobular recess dimensions in millimeters.
T-size	A (mm)	B (mm)
T1	0.90	0.60
T2	1.00	0.70
T3	1.20	0.85
T4	1.35	1.00
T5	1.50	1.10
T6	1.75	1.27
T7	2.10	1.50
T8	2.40	1.75
T9	2.60	1.90
T10	2.80	2.05
T15	3.35	2.40
T20	3.95	2.85
T25	4.50	3.25
T27	5.10	3.68
T30	5.60	4.05
T40	6.75	4.85
T45	7.93	5.64
T50	8.95	6.45
T55	11.35	8.05
T60	13.45	9.60
T70	15.70	11.20
T80	17.75	12.80
T90	20.20	14.40
T100	22.40	16.00

The ISO standard covers recess geometry and inspection, and explicitly is not a manufacturing standard. Source: ISO 10664:2014.

Which Torx Sizes Are Common?

Common ranges depend on the screw manufacturer and industry. These are examples, not a guaranteed screw-thread-to-bit conversion:

T1–T10Small electronics, devices and precision assemblies.

T15–T30General-purpose fastening, decking and many automotive components.

T40–T60Larger mechanical and automotive fasteners.

T70–T100Large or specialized heavy-equipment fasteners.

Do not interchange sizes. T25 is not interchangeable with T27 even if both enter the recess. A T25 bit may fit a standard screw, but it cannot tell you the thread diameter or tightening torque.

Torx Bit Size FAQs

What size is a T25 Torx bit in mm and inches?

The approximate driver tip is 4.43 mm (0.174 in converted). The nominal ISO screw recess A for T25 is 4.50 mm (0.177 in). These are different measurements.

How large is a T30 Torx bit?

About 5.52 mm (0.217 in) across opposite bit-tip lobes. The T30 screw recess has a nominal ISO A width of 5.60 mm.

What are the most common Torx bit sizes?

Commonly used sizes include T10, T15, T20, T25, T27, T30 and T40, though the correct size is determined by the fastener.

Are Torx bits metric or SAE?

Torx bits use T-number size designations, not a direct metric or inch wrench-size designation. Metric and inch figures in this chart are reference measurements, not alternate T-size names.

Does a T25 bit fit a T27 screw?

No. A smaller bit might physically enter but can damage the drive. Use the corresponding driver profile and size.

Is E10 the same as T10?

No. T10 is an internal Torx bit size; E10 identifies an external Torx socket size. The same numeric label does not mean the tools have the same dimensions.

Is security Torx the same size as standard Torx?

Common six-lobe security Torx drives retain the T-size family but add a center post. The matching driver has a center hole. The correct size still matters.

Can I determine a Torx size from the screw thread diameter?

Not reliably. A given screw diameter may be sold with multiple head or drive styles. Use the manufacturer’s fastener specification or physical drive fit.

Sources and Measurement Notes

Data provenance: approximate driver point-to-point widths are published by TORX Products; nominal internal recess A/B dimensions follow ISO 10664:2014. Inch values are calculated from the listed millimeter figures and rounded to three decimals. Dimensions vary by tool supplier and tolerances; select a bit by verified drive family and physical fit.

TORX Products — Products and drive-size dimensions. Source of the approximate T1–T100 driver point-to-point measurements (metric).
ISO 10664:2014 — Hexalobular internal driving feature for bolts and screws. Source for nominal internal recess A and B dimensions. Confirmed current by ISO in 2024.
iFixit — Torx and Torx Plus fit and identification. Additional practical context on drive-family compatibility and fully seated tools.

Compare other drives and fasteners: Allen Wrench Size Chart · Socket Size Chart · Bolt Head Size Chart.