# How to read a tape measure



## bri762 (Nov 1, 2007)

Here is my question. Im pullng a 50' offset to bottom of pond that was a flat land measurement. Now im trying to get the 50' offset back with a 3 to 1 slope. What is the formula with the 3 to 1 slope or a 4 to 1 slope etc....
Thanks


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## neolitic (Apr 20, 2006)

Plumb down from a level tape. That was the pre-laser, pre-computer way. Still works.


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## bri762 (Nov 1, 2007)

im just looking the formula?? Thanks


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## Chris Johnson (Apr 19, 2007)

Pathagorian (sp?) theory. A^2xB^2=C^2

You already know A^2, set up your transit for B^2 then calc out C^2


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## neolitic (Apr 20, 2006)

The sum of the squares of the two sides ( the 50' horizontal and the vertical measurement ) equals the square of the hypotenuse (the measurement up the slope). But really the simple way (and more accurate) is to pull the tape level, and use a bob to plumb down. I've pulled accurate measurements over a mile this way.


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## bri762 (Nov 1, 2007)

I thank you verry much!!


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## A W Smith (Oct 14, 2007)

got a rafter framing square?


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## MVH (Jun 24, 2007)

I am amazed at the number of people the apply for a job and can't read a tape measure. Last guy I worked for hired two for me to supervise, slows the job up pretty well.

Another time I'm squaring a 30x40 footprint with a block guy and his helper. I say, "Lets use two tapes." He looks puzzled. We pin a 30' leg and I say you stand at this pin and your helper stand at that pin and we'll run a tape from both to a third corner. I run the 40' leg and ask the guy on the diagonal how long should his tape read? "I don't know." 50', man!! 3,4,5... 6,8,10 right angles! The block guy goes, "What are you, a mathMAGICIAN." Yeah, thats me, a mathmagician.


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## neolitic (Apr 20, 2006)

MVH said:


> I am amazed at the number of people the apply for a job and can't read a tape measure. Last guy I worked for hired two for me to supervise, slows the job up pretty well.
> 
> Another time I'm squaring a 30x40 footprint with a block guy and his helper. I say, "Lets use two tapes." He looks puzzled. We pin a 30' leg and I say you stand at this pin and your helper stand at that pin and we'll run a tape from both to a third corner. I run the 40' leg and ask the guy on the diagonal how long should his tape read? "I don't know." 50', man!! 3,4,5... 6,8,10 right angles! The block guy goes, "What are you, a mathMAGICIAN." Yeah, thats me, a mathmagician.


It's 5,5 & 7.0711 to an engineer man!


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## firemike (Dec 11, 2005)

If it helps, a 4:1 slope is 14.04 degrees, a 3:1 slope is 18.4 degrees.


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## kgphoto (May 9, 2006)

So what is the formula to convert 3:1 slope to find 18.4 degrees? I just look it up on my speed square or a chart.


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## A W Smith (Oct 14, 2007)

OK just realized a grade or excavating contractor won't have a rafter framing square with all its associated tables. 

The answer is 52.708333 feet. or 632 1/2 inches


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## kgphoto (May 9, 2006)

AW,

I may not be understanding the problem correctly. Are you trying to find the diagonal of a 50 foot run and a 3:1 rise(3 inches rise per foot of run)?

If so, I come up with a 602 1/16" answer or 50 feet and 2 1/16" answer using a construction master calculator. A^2 + B^2 = c^2 where A= 50 inches and B= 600 inches.



Could you sketch what we are trying to find out and what your math was that came up to your answer? I don't know how to link drawings very well so sorry for the oversize paper on this one.

Thank you.


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## neolitic (Apr 20, 2006)

He's running _dirt grades_, not a roof. Try feet.


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## A W Smith (Oct 14, 2007)

No that would be 4 inches in a foot for your 3 to 1 ratio. 12 being divisible by 4 three times.


maybe I misunderstood the question
52 feet 8 1/2 inches is the run of the slope. 
16 feet 8 inches it the change in altitude


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## rino1494 (Jan 31, 2006)

To find the length of the slope on a 3:1, take the horizontal distance and mulitply it by 5%. 

50 x 1.05 = 52.5


For a 4:1 slope, multiply horizontal distance by 3%.

50 x 1.03 = 51.5


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## rino1494 (Jan 31, 2006)

BTW.....if you need to know other slopes, let me know. I know from 1:1 - 6:1


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## kgphoto (May 9, 2006)

OK so it is 1 foot rise for 3 feet of run as opposed to 3 inches of rise per foot of run?

I can see I was way off anyway 3 inches per foot x 50 feet equals 150 inches.
That returns 51 feet 6 7/16 inches. Don't know how I came up with 50 inches.

Only goes to prove the old axiom. GIGO for computers. If you don't understand the question, how ya gonna git the answer?

If it is 1 foot rise for each 3 foot of travel then = 16.6667 rise = 52' -8 7/16"

Thanks for all the responses. I try to learn something everyday.

Still waiting to find the formula to convert ratio's to degrees. I.E. 4/12 pitch(4 inches per foot) for roof is 18.43 degrees. 3 feet run to 1 foot(grade) rise is also 18.43 degrees. Imagine that.


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## neolitic (Apr 20, 2006)

kgphoto said:


> OK so it is 1 foot rise for 3 feet of run as opposed to 3 inches of rise per foot of run?..... I.E. 4/12 pitch(4 inches per foot) for roof is 18.43 degrees. 3 feet run to 1 foot(grade) rise is also 18.43 degrees. Imagine that.


They are both 3:1!


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## A W Smith (Oct 14, 2007)

kgphoto said:


> OK so it is 1 foot rise for 3 feet of run as opposed to 3 inches of rise per foot of run?


 again 3 inches per foot is 3/12 rise, which is 1/4 not 1/3. Ratio and proportion
4/12 = 1/3


> I can see I was way off anyway 3 inches per foot x 50 feet equals 150 inches.
> That returns 51 feet 6 7/16 inches. Don't know how I came up with 50 inches.
> 
> Only goes to prove the old axiom. GIGO for computers. If you don't understand the question, how ya gonna git the answer?
> ...


My square has tables on it. On the wide part of the square (the blade) on the corner are the words 'length of common rafters per foot run". Knowing that a 1/3 pitch is 4 inches rise for 12 inches of run or 4/12 pitch I moved my finger over to the four inch mark on the blade. Under that 4 inch mark I found 12.65. Thats all I needed for my very simple basic math calculations. 
The framing square has many tables on it. Board feet calculators, Rafter hip Vally and jack tables. An octagon scale. A diagonal scale for things like knee braces. You might say it was the first construction master calculator.


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