SCREWDRIVER BIT REFERENCE

Screwdriver Bit Size Chart: PH, PZ, Torx & Hex

Match Phillips (PH), Pozidriv (PZ), Torx (T) and hex (H) bit sizes to the screw in front of you — and confirm the 1/4″ hex shank, working length and hardness your application expects.

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BIT SIZE BASICS

Screwdriver Bit Size Chart at a Glance

Four profiles cover most of the work: Phillips (PH), Pozidriv (PZ), Torx (T) and hex (H). Each uses its own size scale, and most bits mount on a 1/4″ hex shank (DIN ISO 1173 / C 6.3).

THE FOUR CORE PROFILES

What Each Bit Type Is For

4 Profiles

PHILLIPS (PH) Cross head

Designed for controlled cam-out. PH2 is the everyday workhorse.

POZIDRIV (PZ) Cross + 45° ribs

Higher torque with less cam-out. PZ2 is the European standard.

TORX (T) Six-point star

Resists cam-out at high torque. T20 and T25 dominate most sets.

HEX (H) Hexagon

Measured across flats. 2–10 mm covers most metric work.

PH2 and PZ2 are not interchangeable.

A Phillips bit does not seat in a Pozidriv screw, and a Pozidriv bit does not seat in a Phillips screw. Mixing them strips the head.

5-STEP MATCH

How to Match a Bit to a Screw

Confirm the profile, then the size, then the shank before you drive the fastener.

Identify the Recess Profile

Look at the recess shape first. A plain cross is Phillips; a cross with a lighter second cross at 45° is Pozidriv; a six-point star is Torx; a plain hexagon is hex.

Confirm PH or PZ

Cross-head is the most common mix-up. Check for the 45° ribs before choosing a bit — PH and PZ are separate scales and separate tools.

Select the Size

Match the bit number to the screw head: PH2 to general wood screws, T25 to automotive interior work, 4 mm to furniture cam bolts.

Check the Shank and Length

Most interchangeable bits use a 1/4″ hex shank (C 6.3 under DIN ISO 1173). Choose 25 mm for hand drivers and 50 mm for impact drivers.

Stop If the Bit Rocks

A bit that wobbles in the recess is the wrong size or the wrong profile. Under load it will cam out and round the screw head.

CROSS HEAD

Phillips (PH) Bit Sizes

Phillips is the cross-head profile most buyers recognize first. The tip is designed for controlled cam-out, so the driver releases before the fastener is over-tightened or the head is damaged.

Size	Approx. Tip Width	Typical Fastener
PH0	~2 mm	Small electronics screws
PH1	2.5–3 mm	Cabinet hardware, small wood screws
PH2	3.5–5 mm	General wood and drywall screws
PH3	~6 mm	Large construction and decking screws
PH4	~8 mm	Heavy timber and machinery screws

WORKHORSE SIZE PH2 anchors most bit sets.

Precision sizes run PH000, PH00 and PH0 for electronics, eyeglasses and small appliances. Standard sizes run PH0 through PH4, and PH2 is the single most-used size in everyday assembly.

MOST USED PH2

GENERAL RANGE PH0–PH4

Tip widths are approximate — confirm the exact dimensions of your SKU against the relevant standard before publishing a claim.

CROSS HEAD + RIBS

Pozidriv (PZ) Bit Sizes — and Why PZ Is Not PH

Pozidriv looks like Phillips at a glance, and that is exactly where buyers get burned. PZ adds four ribs at 45° between the main cross slots, which increases contact area and allows higher torque with less cam-out.

Size	Typical Fastener
PZ0	Small appliances and electronics
PZ1	Light furniture and hardware
PZ2	Flatpack furniture, general assembly
PZ3	Larger structural and furniture screws
PZ4	Heavy structural and timber screws

CRITICAL DIFFERENCE A PH bit does not seat in a PZ screw.

A Pozidriv bit does not seat in a Phillips screw either. The result of mixing them is a stripped head and a ruined fastener.

Look for 45° ribs

Then specify PZ

If the screw head shows a second, lighter cross etched at 45°, it is Pozidriv. PZ2 is the standard for European flatpack furniture and most general assembly in PZ markets.

SIX-POINT STAR

Torx Bit Size Chart (Including Security Torx)

Torx is a six-point star drive that resists cam-out at high torque, which is why it now dominates automotive, appliance and power-tool assembly. The full scale runs T1 to T100, but the sizes that matter in a working set are narrower.

Size	Typical Fastener / Application
T10	Electronics, small appliance screws
T15	Interior trim, light assembly
T20	General assembly, appliances
T25	Automotive interior, construction
T27	Automotive and equipment fasteners
T30	Automotive, larger equipment
T40	M8–M10 fasteners, brake and suspension

SECURITY TORX Tamper-proof Torx needs a hollow bit.

Security Torx adds a centre pin that blocks a standard bit. Markings vary by maker — TR10 / TT10 or T10H — so confirm the exact convention with the supplier before you order.

STANDARD T20

SECURITY T20H

T20 and T25 are the workhorses. T40 suits M8–M10 fasteners and appears in brake and suspension work.

HEXAGON

Hex (Allen) Bit Sizes — Metric and SAE

Hex bits are measured across flats (AF) — the distance between two parallel flat faces. Metric and SAE (fractional inch) are two separate scales and do not line up cleanly, so a range built for one market may not serve another.

Metric (mm)	SAE (in)	Typical Use
1.5 / 2	1/16″ / 5/64″	Small precision and electronics
2.5	3/32″	Light precision and trim work
3	1/8″	Bicycle, small machinery
4	5/32″	Furniture cam bolts, appliances
5	3/16″	General machinery
6	1/4″	Heavy equipment, automotive
7 / 8	5/16″ / 3/8″	Larger machinery and structural work
10 / 12	3/8″ / 1/2″	Heavy machinery and equipment

TWO SCALES Metric and fractional hex do not line up cleanly.

Common metric sizes run 1.5, 2, 2.5, 3, 4, 5, 5.5, 6, 7, 8, 10 and 12 mm — with 2–10 mm covering most work. Fractional sizes run 5/64″ through 5/32″.

METRIC 2–10 mm

SAE 5/64–5/32″

If your market mixes metric and imperial fasteners, confirm which scale a given spec lands on before ordering.

SINGLE SLOT

Slotted Bit Sizes

Slotted (flat-head) bits are sized by blade width in millimetres, not by a coded scale. They are common in light electrical work but cam out easily under torque, which is why they are rarely used for high-torque assembly.

Match the blade width to the screw slot as closely as possible — an undersized blade rocks and damages the slot. Common widths are shown below; broader ranges also carry 2, 2.5, 3.5, 4.5, 6 and 8 mm.

3 mm 4 mm 5 mm 5.5 mm 6.5 mm

MOUNTING

Bit Shank Sizes and Lengths

The shank is the hexagon that mounts into the driver or drill chuck. Nearly all interchangeable bits use a 1/4″ hex shank, specified as C 6.3 under DIN ISO 1173.

Length	Primary Use
25 mm	Hand drivers, bit holders
50 mm	Cordless drills and impact drivers
75–175 mm	Recessed and long-reach access

SHANK STANDARD Nearly all bits share one mounting size.

The 1/4″ hex shank is the 6.3 mm hexagonal mounting end common to almost every interchangeable bit. It fits bit holders, drills and impact drivers alike.

SHANK 1/4″

STANDARD C 6.3

25 mm is the most common length for hand use, while 50 mm gives impact drivers enough reach to clear the chuck.

BEFORE YOU SPECIFY

Bit Material and Hardness The Size Chart Only Matters If the Bit Survives

Two material grades dominate interchangeable bits, and both need the right hardness band. A correctly sized bit that deforms or snaps fails the customer just as badly as the wrong profile.

GRADE + HARDNESS

Good Bits Land Between 58 and 62 HRC

Softer bits deform and round out under load. Harder bits become brittle and snap. The working band for a dependable bit is narrow, and it is what separates a consumable from a warranty claim.

TOO SOFT Below 58 HRC Deforms and rounds out

→

CORRECT BAND 58–62 HRC Hard, wear-resistant, not brittle

Match the grade to the driver.

Power drivers and impact drivers place different shock loads on a bit than a hand driver does. Specify the grade for the tool the bit will be driven by.

S2 Tool Steel

IMPACT

Tougher under shock loads and the standard grade for power-driver bits. S2 is the usual choice where the bit will see an impact driver or a high-torque cordless drill.

Impact-Rated Shock Resistant Power Drivers

Chrome-Vanadium (Cr-V)

HAND

Hard and wear-resistant, and the common grade for hand-driver bits. Cr-V holds its edge well in steady, non-impact applications.

Wear Resistant Hand Drivers General Use

Hardness Band

58–62 HRC

Softer bits deform and round out; harder bits become brittle and snap. The working band is what keeps a bit in service through its expected life.

Too Soft

58–62 HRC

Too Hard

PRACTICAL RULE Match the profile and size first, then confirm the material and hardness for the driver in use.

A bit that is correctly sized but too soft will round out in the customer’s hand. Specify the grade and the hardness band together, and confirm both against the exact SKU before publishing a performance claim.

FINAL CHECK Grade + HRC

Frequently Asked Questions (FAQs)

The questions that come up most often when a buyer is specifying a screwdriver bit range — profile, size, shank and grade.

Ask an expert

What is the difference between PH2 and PZ2?

PH2 is a Phillips cross head; PZ2 is a Pozidriv cross head with four additional ribs at 45°. They look similar but are not interchangeable — using one in the other’s screw strips the head.

What Torx bit size should I stock?

T20 and T25 cover most assembly and automotive work and should anchor any range. Add T10 and T15 for electronics, and T30 and T40 for larger fasteners.

What is a 1/4″ hex shank?

It is the 6.3 mm hexagonal mounting end common to nearly all interchangeable bits, specified as C 6.3 under DIN ISO 1173. It fits bit holders, drills and impact drivers alike.

What length bit do I need for an impact driver?

50 mm is the standard length for impact drivers, giving enough reach to clear the chuck. Use 25 mm for hand drivers and 75–175 mm for recessed access.

Are security Torx bits different from regular Torx?

Yes. Security Torx adds a centre pin that blocks a standard bit, and requires a matching hollow bit. Markings vary — TR, TT or an “H” suffix — so confirm the convention with the supplier.