# Pythagorean Theorem for finding Gable Rafter Length…Applied Math

thanks for joining me today today I want to go over how to find roof rafter length using Pythagorean theorem if I even said that right who cares but anyway a squared plus B squared equals C squared I've already showed you how to use this and do the step today I'm going to show you how to do the math and figure it out as long as you know the run and the rise in other words we're going to use a four foot span of the building and you take two of that to find a gable rafter so it's going to be 24 inches 2 feet is 24 inches run and it's going to be an 8 12 pitch to roof meaning for every foot the roof is gonna rise 8 inches so 2 feet is gonna rise or roof 16 inches so knowing that the rise of 16 inches and the runs 24 inches let me show you how we come up with the rafter length all right let's get into the math and a 12 pitch roof so remember I said we were going to use a 4 foot on four foot run total so when you do a gable rafter you divide the total run in half and that's how you find your rafter so 2 feet is 24 inches and it's a 812 so every foot it rises 8 inches so we got a 16 inch rise so how do we get the rafter length so Pythagorean theorem is a squared plus B squared equals C squared so a squared which is 24 is 576 sixteen squared is to rise its 256 it equals eight thirty to get the square root it's 28 point eighty four and you convert that to inches and that's gonna be roughly 28 and 7/8 of an inch and then yeah Jordan I'm doing a video you're welcome say hey do you want to say hello on my YouTube video so then 24 is the run 16 is a rise in 28 and 7/8 now I'm going to show you in the book where this number is true so if I go to a 12 pitch roof and look up 2 feet you can see it's 28 Friday at your endpoint right here 28 and 7/8 of an inch and that's it not to lay that out with the square what I would do is you put 8 and 12 on the edge of your board that book is a cheat yeah how you know that because ok well we're not gonna cheat anyway 8 is right here and 12 is here I don't want to really get into this you would mark here you would on pull the tape from the top of this point 28 and 7/8 over and you would do it again with your frames you want to do it with the frame square you just come here if you didn't have a regular square and you go to 8 to 8 for common rafters see common rafters is right here that's 8 I got it lined up and you can work the same angle right here and then you can measure over Oh Lord did she really go there alright so that's the video for today alright today you learn how to use that's right Pythagorean theorem and I hope it helped you I don't use this method but you can use this method to calculate if you don't use the for afters you can use it for from anything in math and he knows that because of this heat book that is my cheap book for sure but anyway when I was in school I would always want to I'm never gonna use that in real life but for your teacher this would be excellent video to show your class applied math how to use Pythagoras theorem in real life thanks for watching have a great day Happy Easter and subscribe comment down below do I have a great day I'm Chris I'm Jordan see you later I'm watching you