Drill bit sizes

Having the right drill bit sizes on hand for your particular repair or building task is essential for any seasoned carpenter or weekend-DIY’er. Knowing just what size you need to use for the hole you’re making is also important, and it may not be totally evident at first glance. Finally, getting the right size  drill bit set in your greater tool “chest” will arm you for the types of projects you’re doing. We’ll discuss these in detail in this article.

How many drill bit sizes are there?
First things first. If you were to look at the most all encompassing collection of multi-purpose, twist-type bits, how many drill bit sizes would there be? Well, if you base your answer on how many size holes are there in the world, then there would be infinite bits! But if we narrow it down to the basic sizes used in the following: everyday home repair and construction projects, hobby, marine, farming, woodworking, metal working, aircraft, arts and crafts, commercial building projects…etc.!, then you would probably just see dozens of required drill bit sizes as it pertains to any particular niche. In fact, most nice sets include anywhere from 12-30 pieces of standardized sizes. (And much more when you factor in different types of bits).

For the sake of simplicity, let’s look at a basic multi-purpose set. One that could serve any of the above mentioned disciplines well overall. Say, for example, a typical 29-piece set, this is what the sizes would include those in the following chart. This would generally apply to many drill bit types, such as black oxide, titanium, carbide, high-speed steel and masonry (concrete) to name a few.

Basic, twist-type drill bit sizes:

  • 1/16″,
  • 5/64″
  • 3/32″,
  • 7/64″
  • 1/8″
  • 9/64″
  • 5/32″
  • 11/64″
  • 3/16″
  • 13/64″
  • 7/32″
  • 15/64″
  • 1/4″
  • 17/64″
  • 9/32″
  • 19/64″
  • 5/16″
  • 21/64″
  • 11/32″
  • 23/64″
  • 3/8″
  • 25/64″
  • 13/32″
  • 27/64″
  • 7/16″
  • 29/64″
  • 15/32″
  • 31/64″
  • 1/2″

There are indeed larger sets. Specialty fasteners sometimes call for a size that would be considered uncommon. Sets with even more varying drill bit sizes would include diameters smaller than 1/16″ or larger than 1-1/2″.

Here would be the standard drill bit sizes for spade bits (13-pieces):

  • 1/4″, 3/8″, 1/2″, 9/16″, 5/8″, 11/16″, 3/4″, 7/8″, 1″, 1-1/8″, 1-1/4″, 1-3/8″ and 1-1/2″

And sizes for step drill bits:

  • Range from 1/8″ to 1-3/8″

large-drill-bit-sizesStandard large bit set

If you need drill bit sizes that are larger than 1″, you can often use a spade bit for wood and other soft materials. To avoid break-outs and chipping, you can stick to bigger round-shank types. For shank bits though, you’ll usually need a

  • 1/2; 33/64; 17/32; 35/64; 9/16; 37/64; 19/32; 39/64; 5/8; 41/64; 21/32; 43/64; 11/16; 45/64; 23/32; 47/64; 3/4; 49/64; 25/32; 51/64; 13/16; 53/64; 27/32; 55/64; 7/8; 57/64; 29/32; 59/64; 15/16; 61/64; 31/32; 63/64; 1; 1-1/8; 1-1/4; 1-3/8; 1-1/2

How do you know what size drill bits you need?
If you’re an average weekend-warrior, you’ve probably stared at a screw or bolt for a few moments and wonder what size drill bit you would need. Over time, you get so that you can literally eye-ball it and make an educated guess. But if you’re looking at a less common drill bit size, you need an aid to help you.

A drill bit size hole card can be very helpful for this. A simple sheet with perfect round holes and markings on it lets you do a couple of things. First, you can size screws simply by inserting them into a hole then reading the marking. You can also size drill bits but pushing them through holes. This is especially helpful if you can’t read the engraved size markings on the bits.

To make things just a little more complicated, not all drill bit sizes are in north american fractional measurements. The metric system is used to define sizes as well. If you have this set, or need to match, just use a simple formula to convert from metric to fractional inches, and vice versa:

  • Converting from millimeters into inches: multiple by 0.039
  • Converting from inches to millimeters: multiply by 25.4

If you’re curious what size drill bit you’ll need for a particular screw, use the following chart:

Screw Size

  • #1
  • #2
  • #3
  • #4
  • #5
  • #6
  • #7
  • #8
  • #9
  • #10
  • #11
  • #12
Hole to clear screw

  • 5/64
  • 3/32
  • 7/64
  • 1/8
  • 1/8
  • 9/64
  • 5/32
  • 11/64
  • 11/64
  • 3/16
  • 3/16
  • 7/32

More about dill bit sets and sizing
Some other helpful information to help you in your knowledge of drill bit sizes:

  • Fractional sizing uses whole, half (1/2), quarter (1/4), eighth (1/8), sixteenths (1/16) and sixty-forths (1/64). For example, something just above 31/64″ would be a half-inch, and anything above 63/64″ would be an inch drill bit size
  • Drill bit lengths i.e. long boy sizes have typical lengths of: 12″ or 18″ overall length. These are handy in situations where you need to drill through thick or multi-layered materials such as in the electrical industry. Standard bits have the following lengths: 1- 1/2″ to 4-3/4″
  • The typical size of drill bit point angles are 115° or 118° (degrees)
  • When buying a good set, ensure it contains more than just one of the common (important) size drill bits. Bit do break as they weaken from usage and high amounts of heat

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