If you want to buy a twist drill bit set for home use but aren’t sure what you need, this will hopefully help you.

The range you will generally need for home use is 1/16" to 1/2". Anything smaller than 1/16" will almost certainly break when used in an handheld drill, and typical handheld drills don’t have the power to drive twist drills larger than 1/2". If you need to drill larger holes than that, you will want to get a different type of bit (like a spade bit, forstner bit, or a hole saw).

Drill bits for home and hobby use come in 1/64" steps. While there are finer graduations available (1/128", 1/100", letter drills and so on) those are generally only needed for precision work.

Most homeowner drill bit sets are sold as “14 piece”, “21 piece” or “29 piece” sets. While it’s not standardized what this means, most manufacturers follow a similar pattern. So use this as a guide but verify before you buy that you get what you need.

13 or 14 Piece (1/16" to 1/4")

These contain every size (every 1/64" step) between 1/16" and 1/4". Specifically, the sizes are: 1/16", 5/64", 3/32", 7/64", 1/8", 9/64", 5/32", 11/64", 3/16", 13/64", 7/32", 15/64" and 1/4".

This is 13 pieces - 14 piece sets contain a duplicate 1/8" bit.

I would not recommend these as your only set, because you will need bits larger than 1/4" even for basic tasks like installing a drywall anchor. These are good as replacement sets for small bits that you broke.

14 Piece (1/16" to 1/2")

Every 1/64" step from 1/16" to 5/32", then every 1/16" step up to 3/8", and then a 1/2". This makes for 12 bits. The other two are either duplicates or other sizes. These sets have a lot of gaps, and I would only recommend them if you are on a budget. The difference in price to a 21-piece set is small, but the difference in utility is large.

21 Piece

Every 1/64" step from 1/16" to 1/4", and then a 5/16", 3/8" and 1/2". There are 5 duplicates between 1/16" and 1/4" - which bits are duplicated vary from manufacturer to manufacturer. These are decent all-around sets for home use. They don’t have too many gaps, and give you a lot of duplicates in small sizes, which is great because you don’t have to buy new bits every time you snap one.

29 Piece

These are complete sets from 1/16" to 1/2" (they contain every size). That’s exactly 29 pieces. You don’t get any duplicates. These are great if you use them a lot because it is very useful to have every size, but it is a good idea to get a supplementary 13 piece set to have replacements on hand for the small bits.