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Formulas for measuring pipe fittings

The formula for a 45 is 1.41. If you measure center of pipe to center of pipe (future) what is the measurement? An example would be if the piping were 12" apart (center to center) you would multiply 12" x 1.41 = 16.92" center to center. Now subtract your fitting allowance (this is the distance between the end of the pipe made up in its socket and the actual centerline of the fitting) say for example (it depends on the size of the fitting) the makeup in the fitting was 5/8" and whats left to center is say 1", you would subtract 2" from your 16.92" measurement or 14.92".

Robert O'Connor/NJ


  • Steve GarsonSteve Garson Member Posts: 191
    Formulas for measuring pipe fittings

    I need to change the pitch of a dry return and figure that I will need to create a swivel joint of sorts with two 45* fittings. Can anyone direct me to some charts or formulas to help calculate pipe lengths with fittings?
  • bigughbigugh Member Posts: 406
    nicely stated

    and it works from 1/8" to 36" easy as pie and you can do it constantly with just your tapemeasure! Rulers are kings or magistrates, a good rule is "do not mess with another mans wife, If she is not married to you, she belongs to another man and don't mess with her either.
  • Tony ConnerTony Conner Member Posts: 443

    ... the old Crane chart.

    Another simple way to figure 45* offsets is to lay off the centre to centre measurement on a framing square. If it's 12", then lay your tape measure diagonally across the 12" marks on the blade and tongue (use either the inside scale for both, or the outside - don't go inside on one and outside on the other). You'll get 17". Subtract the take-aways for whatever size 45*s you're working with, and that's the length of pipe that needs to be cut & threaded.

    For not much money, you can pick up a copy of Audel's "Mechanical Trades Pocket Manual". It's the size of a pocket novel, and has a huge range of info in it, including the take-aways for all of the common screwed fittings, up to 2". It's the Swiss Army Knife/Leatherman of trades books.
  • Steve GarsonSteve Garson Member Posts: 191

    Thanks for posting that chart!
  • Tony ConnerTony Conner Member Posts: 549

    ...also makes a folding "Plumber's Rule", with the regular scale on one side, and the length of the 45* offset on the other.

    This, of course, is exactly the same thing as the old Crane chart, just laid out in a straight line instead of curved to fit the page. The rule doesn't give you the take-aways for the various sizes of 45* elbows like the Crane chart does, though. On the other hand, the rule very likely stands up better on job sites.
  • Pipe Chart

    Tony beat me to the post of the pipe chart. Great minds think alike,,,,LOL.

    Keep it in your computer and print a copy then laminate it for job site use. Loose it or ruin it, and it is easy to print another.

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