Updated on November 14, 2022
Have you ever looked at a screwdriver set and thought “There are more sizes than I’ll ever need” only to read reviews and find out they’re incomplete?
Getting a set that has the sizes you need most can often be more important than buying a “full set” that lacks one or two vital sizes. But how do you know when you have all the necessary sizes?
Read on to find out more about the various screwdriver sizes available for the five most common screw head shapes.
Flat Head Screwdriver Sizes
Commonly referred to as a slotted screwdriver, these have the wedge-shaped blade that any child immediately recognizes. You can often use a slotted screwdriver to work heads with a slightly bigger slot or even Phillips (or other cruciform style) heads in a pinch.
Unfortunately, the way flat head screwdrivers are measured can be frustrating, as the thickness of the tip is rarely given. The good news is that the width of the tip and the length of the shank are presented in the measurements provided. These measurements are presented as width by length (for example, 1/8″ x 4″).
The shank length will affect whether the screwdriver can fit into a deeper recess (perfect for automotive work) or if it functions best where there’s very little room for your hand. Note that the length of the handle is proportionate to the length of the shank, so short-shanked drives also have short handles.
See also: Parts of a Screwdriver
Slotted Precision Sizes Chart
| Tip Width (SAE) | Tip Width (Metric) |
|---|---|
| 0.8 mm | |
| 1 mm | |
| 1.2 mm | |
| 1.5 mm | |
| 1.8 mm | |
| 2 mm | |
| 3/32" | 2.5 mm |
| 1/8" | 3 mm |
| 3.5 mm | |
| 5/32" | 4 mm |
Slotted Standard Sizes Chart
| Tip Width (SAE) | Tip Width (Metric) |
|---|---|
| 3/16" | |
| 4.5 mm | |
| 5 mm | |
| 7/32" | 5.5 mm |
| 6 mm | |
| 1/4" | 6.5 mm |
| 5/16" | |
| 3/8" |
Phillips Screwdriver Sizes
This popular cruciform drive has become a standard in many countries. Less prone to slipping than slotted screwdrivers, the design still has some issues at high torque that have since been resolved in newer cruciform designs.
As with slotted screwdrivers, Phillips drives are popular in precision work, being a staple in laptops and other electronics.
To an extent, Phillips screwdrivers may be used on any cruciform screw, although there is an increased risk of cam out and damage to the head. Part of this is the fact that a Phillips driver is sized through a number code instead of an Imperial/SAE measurement and can fit two to five sizes of head above its own.
Phillips Precision Sizes Chart
| Phillips # | Tip Width (Metric) | Fits Screw Sizes |
|---|---|---|
| #0000 | 1 mm | |
| #000 | 1.5 mm | |
| #00 | 2 mm | |
| #0 | 2.5 mm | 0-1 |
| #1 | 3 mm | 2-4 |
Phillips Standard Sizes Chart
| Phillips # | Tip Width (Metric) | Fits Screw Sizes |
|---|---|---|
| #2 | 3.5 mm | 5-9 |
| #3 | 5 mm | 10-14, 16 |
| #4 | 6 mm | 18, 20, 24 |
| #5 | 8 mm | 5/8" and 3/4" (machine screws) |
Pozidriv Screwdriver Sizes
This screw drive is often referred to as an improved version of the Phillips drive. Instead of the Phillips’ pointed tip, tapered flanks, and rounded corners, a Pozidriv has a blunt tip, parallel flanks, and an additional small rib between each slot. This allows for increased grip between the bit and fastener.
While you can fit a Phillips bit in a Pozidriv fastener, it will likely cam-out before you can fully tighten it. A Pozidriv bit will not fit inside a Phillips fastener. Pozidriv bits have a “PZ” marked on them along with five common sizes.
Pozidriv Sizes Chart
| Size # | Wood Screws | Machine/Tapping Screws | Metric Screws |
|---|---|---|---|
| #0 | #0, #1 | #0, #1 | M1.6, M2 |
| #1 | #2, #3, #4 | #2, #3, #4 | M2.5, M3 |
| #2 | #5 to #9 | #5 to #10 | M3.5, M4, M5 |
| #3 | #10 to #16 | #12 (or 1/4", 5/16") | M6 |
| #4 | #18 to #24 | 5/16" to 1/2" | M8, M10 |
Hex Key Screwdriver Sizes
Hex keys are named because they have a smooth hexagonal shank and no head. More commonly referred to as Allen wrenches, these screwdrivers sometimes come in an L-shaped shank with no handle, as multiple retractable sizes with a centrah handle (ala Swiss army knives), or even with a ball-shaped tip.
Measurements for hex keys is done via AF (short for across flats). To measure an unmarked key, for example, you would measure the distance between two opposing ends. This makes it easy to determine the key needed for a specific hex screw when you’re not sure of the size.
Hex Key Sizes Chart
| Tip Width (SAE) | Tip Width (Metric) |
|---|---|
| .7 mm | |
| .9 mm | |
| 3/64" | 1.2 mm |
| 1.3 mm | |
| 1.5 mm | |
| 1/16" | 1.6 mm |
| 5/64" | 2 mm |
| 3/32" | 2.4 mm |
| 2.5 mm | |
| 7/64" | 2.8 mm |
| 3 mm | |
| 1/8" | 3.2 mm |
| 9/64" | 3.5 mm |
| 5/32" | 4 mm |
| 11/64" | 4.4 mm |
| 4.5 mm | |
| 3/16" | 4.8 mm |
| 5 mm | |
| 13/64" | 5.2 mm |
| 7/32" | 5.5 mm |
| 15/64" | 6 mm |
| 1/4" | 6.4 mm |
| 7 mm | |
| 5/16" | 8 mm |
| 9 mm | |
| 3/8" | 9.5 mm |
| 10 mm | |
| 1/2" | 12.7 mm |
Robertson Screwdriver Sizes
Popular in both construction and electrical fields, the Robertson drive (commonly referred to as the square drive) is more common in Canada than the US due to licensing problems earlier in its history.
Now that the original patents and licensing restrictions have begun to expire, Robertson screws are gaining in popularity worldwide.
Much like Phillips screwdrivers, Robertson drives use a numbering system. What sets these apart, however, is that all sizes are also color-coded for easy reference.
Robertson Sizes Chart
| Color Code | Size # | Fits Screw Sizes |
|---|---|---|
| Orange | #00 | 1-2 |
| Yellow | #0 | 3-4 |
| Green | #1 | 5-7 |
| Red | #2 | 8-10 |
| Black | #3 | 12, 1/4" |
| Brown | #4 | 5/16", 3/8" |
Torx Screwdriver Sizes
Sometimes referred to as the star drive due to its rounded 6-point star shape, the Torx drive is designed to function at higher torques and have a longer lifespan than other popular screwdriver types.
This has made them quite popular in both electronics and automotive industries. They can also be used as an emergency substitute for hex drives, although there’s a higher risk of stripping the head.
Torx drives use a numbering system based upon the distance between two opposing points. Unlike other driver measuring systems, the same numbers on a Torx screwdriver apply to both SAE and metric scales.
You can identify the size required for a random screw by measuring the width of the slot and comparing it to a Torx sizing chart.
Torx Sizes Chart
| Torx Size | Width (SAE) | Width (Metric) |
|---|---|---|
| T1 | .031" | .81 mm |
| T2 | .036" | .93 mm |
| T3 | .046" | 1.10 mm |
| T4 | .050" | 1.28 mm |
| T5 | .055" | 1.42 mm |
| T6 | .066" | 1.70 mm |
| T7 | .078" | 1.99 mm |
| T8 | .090" | 2.31 mm |
| T9 | .098" | 2.50 mm |
| T10 | .107" | 2.74 mm |
| T15 | .128" | 3.27 mm |
| T20 | .151" | 3.86 mm |
| T25 | .173" | 4.43 mm |
| T27 | .195" | 4.99 mm |
| T30 | .216" | 5.52 mm |
| T40 | .260" | 6.65 mm |
| T45 | .306" | 7.82 mm |
| T50 | .346" | 8.83 mm |
| T55 | .440" | 11.22 mm |
| T60 | .519" | 13.25 mm |
| T70 | .610" | 15.51 mm |
| T80 | .690" | 17.54 mm |
| T90 | .784" | 19.92 mm |
| T100 | .871" | 22.13 mm |
What is the M2.0 screw refered to in this Lenovo S340 service guide? https://i.imgur.com/3QByFQu.jpg
That would be a machine screw. The 2.0 is the diameter and 8 is the length (both in mm).
Being Canadian having worked with every type of screw out there Robertson are are far and away the best ans seem to be the fastest way to go. Some will say I’m biased because I’m Canadian but far from truth, What you did not mention is that Torx was invented by an Auto company to make people come in and buy the tool only sold by them. There is a new screwdriver out now and I’ve found it mostly in electronics. It looks like Torx but has a knob in the centre of the screw. So far only seen small ones . Thanks for the charts and mentioning colour coating. Actually a great idea. It just seems easier to look for a green or a red rather than searching for size.
Thanks for the comment JK.
You are correct about Torx being invented by an auto manufacturer; General Motors, in fact. They used this “new” screwhead in headlight trim to make it impossible to replace a headlight (back when that was a regular wear item) unless you purchased a tool from the GM stealer, er, um, dealer. The tool was expensive at, IIRC, around $12 which is equivalent to about $40 today. They were a cheaply made screwdriver-style with two sizes available.
Robertson even refused to license, that is really….
Bosch made one type P2R2 bits, its not double ended bit, but one bit fit both PH2
and your beloved RED 2.
Robertson refused to license it to Ford because he had previously license it to a business in England but they went and declared bankruptcy so they could avoid paying the license fee/royalties and then went and started a new company free from license restriction. This unfortunately make Robertson shy away from Ford because it cost him a lot of time and money to fight the English fraudsters and didn’t want to go through that again.
The Phillips head was adopted by Ford and was unfortunately spread through Europe (and the rest of the world) via WWII equipment. I have never used a Robertson but I have read much about it and I have lamented for years about the awful slut, I mean slot head screw and the the commonly “cammed out” Phillips. Oh for a world full of Robertson heads and the drivers of course.
THANK YOU for publishing this page as it is greatly appreciated. No need for photos of each screw head because they will vary in “size” due to different monitors. By putting the size/width of the head it is easily worked out and a $5 digital vernier caliper it makes checking ones screw measurements a doodle. Thanks again!!
If your caliper is digital it’s not Vernier.
Digital, Dial nd Vernier are three different types of readouts.
Digital is the easiest to read, Dial is pretty easy to read, but if your eyesight isn’t sharp the Vernier scale can be difficult if not impossible to read.
How about an actual size photo of every size? A picture is worth a thousand words.
Up vote this comment a million times! Correct, Ruben. I was thinking the same thing.
A photo would be very helpful. A dimensionalized sketch would be even better.
Since this doesn’t address the actual sizes I had to dig out my drivers and measure them myself, I’ll share that information here for the benefit of those who want to know the actual sizes:
R1 = .098″ (approximately 3/32″. Actually .005″ bigger than 3/32″).
R2 = .119″ (Approximately 1/8″. Actually .006″ smaller than 1/8″).
R3 = .141″ (Approximately 9/64″. Almost exactly 9/64″ less than a thousandth of an inch larger than 9/64″ which is exactly .140625″).
If you’re thinking you might find a piece of square stock to substitute for R1 in a pinch, 3/32 square stock will be a loose fit (and may “cam out” or round off especially if not hard stock).
1/8″ square stock may be a force fit (AKA hammer or “pressed fit), for R2 and will possibly ruin the head of the screw or ruin whatever it’s screwed into).
9/64” square stock, (if you can find it), would be a perfect fit for R3, but it should be hardened steel.
“To measure an unmarked key, for example, you would measure the distance between two opposing ends. ”
Would that be between opposing flat faces, or between points?
The flat sides.
points on torx
Flat sides on Robertson, points on Torx.
what’s the size of Pozidriv screwdriver
Updated the article to include Pozidriv sizes.
Please do one for Y-Screws (or Tri-Wing Screws), I’ve literally been searching on & off for YEARS now…-Thanks a lot Nintendo(!)
I concur!!! I don’t understand why it is sooooo difficult to find a size guide for the Tri-wing/tri-point heads! I have been looking everywhere with no success either! Any help would be greatly appreciated!
I get soo confused about the whole ‘difference between a screw’s drive size & screw size’ part 🙁
I appreciate your site as I am trying to make up a set of as many complete sets of drivers complete with individual handles permanently attached as a gift for my son.
I have been in the electrical and basic electronic trade since 1952 as an apprentice tradie anl later in my own small business in which I apprenticed my own two sons, working in industry then after CABGs surgery and a stroke as a teacher. I can’t stop trying to fix things
Thank you.
Thanks for the comment Bill. What a fantastic gift idea for your son. Yes, I’m sure many of our readers can relate as far as having a hard time trying to fix things. I wish you the best.
I have more of a question. My retractable screen door needs the screws replaced, mainly because one is not biting into the wood. I have to repair the wood first, but my question is the company that installed it told me that the screw is a Robertson. I would need Robertson#1 screwdriver to screw it in with once I have repaired the wood. I have stripped the head on the screws because I tried to take them out with an Allen wrench. What other wood screw sizes will fit the opening of a Robertson Screw that would need a #1 screwdriver?
Thanks
Gonzo
Maybe I’m not understanding the question but a Robertson #1 will work with screw sizes #5, #6, and #7.
GM did not invent the Torx. Bernard F. Reiland did.
https://www.legacy.com/obituaries/rrstar/obituary.aspx?n=bernard-reiland&pid=107223629
The development of the Torx screw began in 1967, was patented in 1971 and was invented by Bernard F. Reiland for the then Camcar Textron company.
https://www.hausoftools.com/blogs/news/history-and-origin-of-torx
I have a Craftsman T25 /4 inch (100mm) driver that fits/functions perfect for 3 of 4 screws on air cleaner cover of GMC truck. The 4th screw needs to have a 6 inch shaft to be comfortable for a larger hand to manipulate. Is there a T25 / 6 in.(125mm)? A substitute for Craftsman would be ok just so it has the 6 point star configuration head to fit screw.
A reply would be appreciated. Rob
Hi, my Name is Istvan, I live in Hungary.
I got several pieces screw from Canada with Robertson square. The square is 2,9*2,9mm. My question: which bit size fit into the screw square?
Sounds like a #1 (green) Robertson. Technically it’s for a 2.82mm – 2.86mm square recess but that sounds like what you have. Source
There is no mention of the JIS (Japanese Industrial Standard) screw head. This is the the evil screw on your Japanese carburetor that strips because you thought it was a Phillips.
This would be so much more useful if they were available in PDF format instead of just a blog post. Some of these could be easily hard laminated for DIYer workshop reference material. Peace.
Thanks for the comment. I created PDFs for socket and wrench sizes but found there to be little demand for those. But I’ll try to get around to converting the charts on this page to PDF.
I’ve been researching slotted bits, to order for my job, and I’ve seen a LOT of websites listing their slotted bits as 6F-8R, or 3F-5R, instead of the simple fractional tip sizes. Do you know the cause of this completely stupid and incomprehensible change? By the way, 6F-8R is supposed to represent a 1/4″slotted.
Thank you
It would be great if you could recommend which screwdrivers are useful for day-to-day home use.
For example, seems to me that phillips #0, #1 and #2 will be enough for more than half of the screws I’ll encounter around the house.
What else would you recommend for a basic set?
For the majority of people in the US, a good set of slotted and Phillips screwdrivers would be considered essential. A #2 Phillips will likely be the most used size but a #1 and #3 is necessary for some things. A #0 is nice to have but I wouldn’t consider essential.
For slotted, a 1/4″ would probably be the most common but 3/16″ and 5/16″ are good to have. Something larger like a 3/8″ flat head is good for prying.
I’m a big fan of the 8-piece Klein set if someone wants the essentials and doesn’t mind paying a bit extra for quality.
I’d also recommend a #2 Phillips and 1/4″ slotted “stubby” screwdriver. I personally would consider a good set of Torx bits essential as well. For others, I would purchase on an as-needed basis.
Hi All,
This is some how good information but as someone mentioned before it will be very helpful if you can post a picture with actual dimensions of each screw size, in my case for example I’s strugling to find out which size of a Robertson tip I have buy for a custom screw I have, the table you showed here means nothing to me, the actual size of the square bit I need is a 4×4 mm. Hope someone here can help me find out which bit size is this. Thanks!!
4mm X 4mm is 5/32″ and larger than a R3 by about .016″, (1/64″).I have a set that I measured, but it only includes R1, R2 and R3, I don’t know the size of R4 because my set does not include that size, but they appear to go in increments of approximately 1/64″ or ½mm. I know R1, R2 and R3 are too small, I would guess that R4 should be correct for a 4mm X 4mm recess. I see that this question was asked more than a year ago, but I just found it while searching for a similar answer and had to measure my tools, (I was hoping an internet search would be quicker and easier than digging out my tools). You probably had tour answer a long time ago, but maybe my answer will help someone else with a similar question.
Thanks Jakey!
Hi all
Recently while at the market, I came across three different 1/2 drive sockets with Philips bit #4, in the sense that the tip in one was sharply pointed, in the next one it was a bit rounded, and in the next one more flatter and rounded.
So this left me puzzled as to which one to get, as I was not aware that Philips can be so different with each size
What size Tri-point or “Y” driver is comparable to T7 Torx?
Thanks.