I think what you are asking is which do you measure the inside or the outside of the pipe. From your question there doesn't need to be an answer. Usually it is the inside measurement that is meant. The useful part of the pipe or how much it can carry.
Three 0.50 inch diameter pipes will fit into one 1.50 inch diameter pipe (hypothetically). The 0.50 inch diameters stack on top of each other until you have 1.50 inches!
1/2 inch + 2*thickness of the pipe.
this depends on the class of the pipe as the higher the class the thicker the pipe
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It takes 24.50985 feet of 1 inch pipe to hold one gallon of water. Jeff Payne jpayne@texwipe.com
A three-inch diameter pipe one foot long holds 0.367 gallon.
The weight of the pipe will depend on its volume, The volume in turn, will depend oninner radius or diameter,outer radius or diameter,length.Only one of these is given.
If I remember correctly, the pipe size is the inside diameter, so it would depend on the thickness of the wall, as to what size it would fit into.
The take-off for a standard radius 90 is one and one half the diameter of the pipe. Example: 6 inch 90 has a take- off of 9 inches. The take-off for short radius 90 would be the dia. of the pipe. Long radius 90 is 2 times the pipe diameter.
pi x (42 - 12 - 12)/4 x 1/144 x 65 = 4.963 ft3
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Pipe threads are stated in terms of so many threads per inch. For instance, a bolt designated as 1/4-20 is a 1/4 inch diameter bolt with 20 threads per inch. Divide one inch by 20 to find the pitch distance.