Napier's Bones: Quickly Multiply, Wooden Style

I first encountered Napier's Bones back in Mrs. Hutnick's 4th grade EL math class. We had a 'build day' of sorts in which we made our own Napier's Bones, and at the time I thought they were really cool. Now, a bunch of years later, I still think they're really cool--they're very simple to make and to use, they are durable, and they can be personalized in any way you see fit.

My old pair is quite sloppy (though not bad for a 10-year-old, I'd say. Good job, former me), so I decided to make a new and improved set--documented here on Instructables.

Now for the important part: what Napier's Bones are. They are a multiplication tool/math toy that allows you to multiply 0-9 with large numbers extremely quickly with only slabs of wood. As long as you add small numbers and read correctly, you will get the correct solution every time.
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Step 1: How They Work

Picture of How They Work
Watch the video below while relaxing to the smooth tunes in the background:

Step 2: Materials

You'll need:

Wood. Unless you have a table saw to cut wood lengthwise, your best bet will be to get 1" x 1" or 3/4" x 3/4" poles. You will need at least 30 inches of wood, but more likely around 50 inches if you want the ability to mulitply more numbers. The wood needs to be square.

Hardboard. Also called Masonite, you need a piece 10 inches high by approximately 4 inches. I got a 10 x 14 sheet and cut it in one direction.

Wood Glue, and a clamp to keep pressure while it dries.

Sharpie Markers. If you want a different look, you can use some other writing/painting instrument.

A saw (I used circular) and sandpaper.
Minimal1 year ago
This is actually how I learned long multiplication ( using lattice multiplication, not this toy ). I wish I had thought of this when I was teaching it to my daughter. Would have been a great way to illustrate.

That said, I also initially failed a math test in high school because my trig teacher couldn't "read my work" and told me she didn't believe that my lattices were actually math.

Then I had to teach the class how to do lattice multiplication before she'd correct the grade.
 I love this kind of stuff , Thank you, now am off to the shop to build my own
I actually made it into foam board.
E-R-IC6 years ago
can you multiply more digits?
joshf (author)  E-R-IC6 years ago
if you make more bones, you can multiply more digits.
E-R-IC joshf6 years ago
thanks for the fast answear
This is great. I love playing with numbers (and I work with them a fair bit). This really wet my appetite, so I looked up some more info:

It adds to your explanation, and tells of more things we can do with it, making your Instrucatable even more valuable!
very helpful
E-R-IC6 years ago
this pic might help:
Cinders20016 years ago
Very well put together.....I just need to learn how to use them!! Probably easier than I thinkt....but i'm thick!! Thanks.
as noted below, wikipedia explains.
bruno130696 years ago
Sometimes I'll draw a "Napier's grid" to do multiplication instead of trying to line-up all of the columns vertically. The first time I did this, I got weird looks from some friends, but I was doing (6 figure * 6 figure) multiplications faster than the rest of them.
frkohler6 years ago
Muito legal!!! Muito mais fácil de usar que o ábaco! Congratulações!
hammer98766 years ago
I love this! I'm thinking of building a couple of sets for my puzzle loving nephews. They should get a kick out of it. OK. It isn't a puzzle, I realize that, but because they like puzzles, we have the material because we keep making stuff for them. I am thinking though, that it would be great if the wood could be finished.
mattdonahoe6 years ago
Mrs. Hutnick? Nice. By the time they let me in her EL math class, it was the end of fifth grade and we were playing with platonic solids.
capricorn6 years ago
I love that :) Will do as soon i find the wood ;)
hornbadoing6 years ago
my new fevered Instructable
Doctor What6 years ago
I had to watch the video twice, but I get it. This is a really neat project!
And I like your instructions. They are really thorough!
Tinker836 years ago
this is the method that was taught when my dad was in school. i don't recall him saying anything about using a tool like this, but the thought process was the same. it's disgusting how he can spout off a number before i can even get it written down.
Rob K6 years ago
Neat way to do math.
=SMART=6 years ago
I think i get it, ill have to make it and test it out :P Very nice way to work math out though : 5 *
I'm really happy you posted this. I now understand how to use them! I was at a bit of loss while you were working on them. :P