1. [OP] Member
Join Date
Oct 2003
Posts
440

## 3x4x5 method????

Ok, you all already know that I am new to woodworking, so let me in on what exactly is the 3x4x5 method when squaring up plywood?

2. ## 3 x 4 x 5

Measure up one side very accurately 3 inches or feet (the longer measure is more accurate) ,measure up the other side very accurately 4, then measure diagonally between the marks. If it measures 5 exactly, your piece is square (you are measuring the long side of a triangle).
Hope this is clear, it's too early for much geometry.
Eddie

3. Originally Posted by aurelio alarcon
Ok, you all already know that I am new to woodworking, so let me in on what exactly is the 3x4x5 method when squaring up plywood?
This method uses the so-called Pythagoras c² = a² + b²

So if you have a rectangular piece of ply, one side is 3", the other is 4", the diagonal has to be 5".

Hope this helps,

Christian

4. You can also use the 2, 3 and 3.6055512754639892931192212674705 method, but for some reason it is not so popular.

5. Rob - that was funny!

6. Rob,

LMAO

7. 6, 8, 10 and 5, 12, 13 are also usable options.

8. [OP] Member
Join Date
Oct 2003
Posts
440

## thanks guys!

Thanks guys. I think I remember Norm doing this.

9. Originally Posted by Christian Aufreiter
Hope this helps,

Christian
Hey Christian.....I didn't realize you were in Austria until this morning.

I have been to Austria several year ago...been through Insbrook (spelling?).....really pretty place.

10. Originally Posted by Rob Glynn
You can also use the 2, 3 and 3.6055512754639892931192212674705 method, but for some reason it is not so popular.
Hey Rob....I think you were off one digit..?

11. Originally Posted by Dennis Peacock
Hey Christian.....I didn't realize you were in Austria until this morning.

I have been to Austria several year ago...been through Insbrook (spelling?).....really pretty place.
Hi Dennis,

what did you do in Austria, did you visit it for a special reason?
As you mentioned Innsbruck ("Inn" is a river), did you stop at the Felder company?
You probably remember the "Goldene Dachl" (Golden Roof), Innsbruck's landmark.
I live in a small village located near Linz, Upperaustria.

Regards,

Christian

12. Member
Join Date
Feb 2004
Location
Modesto, CA
Posts
2,364

## 3-4-5

Jason mentioned some variations but you can double or halve the 3--4--5 measurements and they will all work. For example, 1-1/2--2--2-1/2 or 3/4--1--1-1/4 or going the other way 6--8--10 or 12--16--20 etc. These measurements can be acres, hectares, furlongs, rods, chains, yards, feet, inches, cubits, paint cans, coffee cups, any units of measure that you care to use as long as they stay the same. On larger scales your measurements can probably be off a smidge and you can get away with it like on floors or patios and such. For smaller areas, under 1.5--2--2.5 let's say, your measurements need to be getting more and more critical the smaller you go. I don't believe that I can see that small a difference, an accurate 1/16" is probably my limit, so I use a known good (perfect 90 degrees) square for anything the size of a framing square or smaller. Just my two cents. Hope it helps.

13. Contributor
Join Date
Mar 2003
Location
San Francisco, CA
Posts
7,927
Originally Posted by Mark Rios
Jason mentioned some variations but you can double or halve the 3--4--5 measurements and they will all work. For example, 1-1/2--2--2-1/2 or 3/4--1--1-1/4 or going the other way 6--8--10 or 12--16--20 etc. These measurements can be acres, hectares, furlongs, rods, chains, yards, feet, inches, cubits, paint cans, coffee cups, any units of measure that you care to use as long as they stay the same. On larger scales your measurements can probably be off a smidge and you can get away with it like on floors or patios and such. For smaller areas, under 1.5--2--2.5 let's say, your measurements need to be getting more and more critical the smaller you go. I don't believe that I can see that small a difference, an accurate 1/16" is probably my limit, so I use a known good (perfect 90 degrees) square for anything the size of a framing square or smaller. Just my two cents. Hope it helps.
Mark --
You're pretty much right, except that the unit of measure needs to be a distance measurement. Furlongs, rods, chains, yards, feet, inches, and cubits work just fine. Acres and hectares do not. They are area measures.
Jamie

And since tomorrow is Sunday - what about cubits???

15. Member
Join Date
Mar 2003
Location
Angels Camp, CA (gold country)
Posts
22

## Cubits?

Todd, my Pocket REF lists 12 different cubits - this could get messy!

Cheers, Larry

Originally Posted by Todd Burch