Screw extractor size chart

Updated 15 November 2026 · 4 min read

Screw extractors are numbered, usually #0 to #5, and each number covers a range of screw sizes. Picking the right one matters: too small and it can snap, too big and it can cut through the head. Here's how to match them.

Our set's size chart

These are the maker's figures for the six bits in our set. "Burr tip" is the size of the cutting end. The screw range is the screw diameter each bit is made for.

Bit	Burr tip	For screws
#0	1.9 mm	2–3 mm
#1	2.8 mm	3–5 mm
#2 (two in the set)	3.4 mm	4–8 mm
#3	4.0 mm	5–10 mm
#4	6.2 mm	6–12 mm

Other brands number their extractors a little differently, so if you're using another set, check its own chart.

The six bits51 mm each · 1/4" hex shank

#4 6.2 mmscrews 6–12 mm
#3 4.0 mmscrews 5–10 mm
#2 3.4 mmscrews 4–8 mm
#2 3.4 mmscrews 4–8 mm
#1 2.8 mmscrews 3–5 mm
#0 1.9 mmscrews 2–3 mm

The six bits in our set, drawn to the maker's sizes.

Find your screw

Australian timber screws are sold by gauge (8g, 10g and so on), and machine screws and bolts by metric size (M4, M6). This table converts both to millimetres and shows which of our bits cover each one.

Screw	Diameter	Start with	Also fits	Usually found in
M2 Machine screw	2.0 mm	#0	-	Laptops, toys, small electronics
M2.5 Machine screw	2.5 mm	#0	-	Laptops, small appliances
4g Wood screw	2.8 mm	#0	-	Small hinges, cabinet hardware
M3 Machine screw	3.0 mm	#0	#1	Appliances, computer cases
6g Wood screw	3.5 mm	#1	-	Cabinet hinges, light fixings
M4 Machine screw	4.0 mm	#1	#2	Appliances, furniture fittings
8g Wood screw	4.2 mm	#1	#2	Door hinges, general timber work
10g Wood or decking screw	4.8 mm	#1	#2	Decking, fence palings, framing
M5 Machine screw or bolt	5.0 mm	#1	#2, #3	Flat-pack furniture, brackets
12g Wood or batten screw	5.5 mm	#2	#3	Battens, heavier timber
M6 Bolt	6.0 mm	#2	#3, #4	Flat-pack bolts, bikes, brackets
14g Roofing or tek screw	6.3 mm	#2	#3, #4	Roof sheeting, steel framing
M8 Bolt	8.0 mm	#2	#3, #4	Cars, trailers, machinery
M10 Bolt	10.0 mm	#3	#4	Cars, trailers, machinery
M12 Bolt	12.0 mm	#4	-	Vehicles, heavy brackets

Wood screw gauges are converted to the nearest tenth of a millimetre. Bits listed are from the maker's ranges above.

If two sizes fit, start small

The ranges overlap, so most screws are covered by two or three bits. Start with the smallest bit that covers your screw. If its burr end skates instead of cutting, or the extractor end spins without biting, go up one size and cut again. You can always make a seat bigger, but never smaller.

The #2 covers the most common screws, from 4 to 8 mm, which is why our set has two of them.

How to measure a screw

Read the box. Timber screws are labelled gauge by length, so "10g × 65 mm" is a 10 gauge screw (about 4.8 mm) that's 65 mm long. Metric bolts are labelled like "M6 × 20".
Find a twin. Screws in hinges, decks and furniture usually come in matching sets. Measure one that isn't stuck.
Measure across the thread. Use a vernier or digital calliper across the outside of the thread, not the head.
Guess from the head. A screw head is usually about twice the screw's diameter. Measure the head and halve it if that's all you can see.

Does the head shape matter?

Not for a double-ended extractor. The burr end cuts its own round seat, so Phillips, Pozidriv, flat, Torx, hex and rounded-off heads are all the same to it. What matters is the screw's diameter. For how to use the bits once you've picked one, see how to use a screw extractor.

Bigger than 12 mm, or smaller than 2 mm

Our set covers screws from 2 to 12 mm. Bolts bigger than that, or bolts with the hex head rounded off, need larger extractors or a bolt extractor socket set. Screws smaller than 2 mm, such as those in phones and glasses, need a precision kit made for electronics.

Questions

What size screw extractor do I need for a 10g screw?

A 10 gauge screw is about 4.8 mm across. In our set the #1 (3 to 5 mm) and #2 (4 to 8 mm) both cover it. Start with the #1 and go up to the #2 if it won't bite.

What size extractor for an 8g screw?

An 8 gauge screw is about 4.2 mm. In our set that's the #1 or the #2. Start with the #1.

What size extractor for an M6 bolt?

M6 is 6 mm. In our set the #2, #3 and #4 all cover it. Start with the #2. If the bolt is high-tensile, it may be too hard for any HSS extractor.

How do I know what size my screw is?

Check the box it came in, measure a matching screw that isn't stuck, or measure across the thread with a calliper. If you can only see the head, the screw is usually about half the head's width.