# What size dowels to use for joints?

I'm comfortable with the process of creating and joining wood with dowels, but I'm not sure what size dowels to use in which cases? Specifically, I'm working with 1" thick stock (3/4" actual), what size should I use?

What are the other sizes and lengths of dowels used for?

Are there any recommended grouping or spacing for wood dowels?

• This would be more at home in the Woodworking stack. Commented May 26 at 5:04

When dealing with joinery I typically always deal with thirds. So I'd get whatever is closest to 1/3" that I can get. 3/8" is probably good for this, 5/16" even better. Thirds is a pretty good rule of thumb especially for furniture sized joinery.

This can be applied to all types of joinery such as mortise and tenon, splined miters, bridle joints, etc.

• +1 also. 1/3 is easier to remember, though with full-size lumber 3/8 is sometimes easier to compute and measure. :) Commented Sep 26, 2011 at 17:34
• Sat in on a class of Roy Underhill's this weekend. His opinion is to use something at least 1/3rd of the thickness of the piece but less than half. Commented Oct 3, 2011 at 19:09
• I don't see how this is the correct answer. If the actual thickness of the wood is 3/4" and the dowels should be 1/3 of this, shouldn't the dowels be 1/4"? A 5/16" dowel would be 1/16" too large, a 3/8" dowel would be 1/8" too large. Commented Jun 1, 2020 at 20:02
• @AaronCicali Agree with rule of thirds but math is wrong. 3/4" * 1/3 = 1/4" Commented Sep 28, 2022 at 16:31
• @franklylately Isn't one third of three quarters equal to one quarter? We seem to be in agreement. Will you please clarify which math is wrong? Thanks! Commented Sep 28, 2022 at 16:36

The best work I know of on the topic was written by Tage Frid (see http://amazon.com).

The approximate rule-of-thumb, iirc, is to use a dowel no more than 3/8 the thickness of the wood to be joined (and not less than 1/4 the thickness).

### Expansion

For example, if you are joining 5/4 boards (finished thickness 1"), the dowels should be between 1/4" and 3/8" in diameter.

Likewise, if joining finished thickness 3/4" boards, use between 3/16" and 9/32" diameter dowels.

This presumes, of course, you're joining the boards on the narrow dimension (e.g. making a door frame).

• This is the publisher's page for the book I'm assuming you're referring to. Also as an ebook. Commented Sep 30, 2010 at 18:10
• @Dennis Williamson - actually, I was thinking of amazon.com/Tage-Teaches-Woodworking-Step---Step/dp/1561588261 Commented Oct 7, 2010 at 18:49
• So, a 4.5mm dowel for a 12mm thick board? Commented Aug 18, 2021 at 17:10
• @MattFletcher - something in that ballpark, yes Commented Aug 18, 2021 at 19:37

Forget about “rules of thumb”. Following them you could end up with 3/4” dowels for two by four size of wood, which would not last long due to dowel shrinkage over time. I would advice to stick to no larger than 3/8” dowels for any wood thickness and put them in several rows in thicker pieces.