How do I calculate what size pipe I need?
How do I calculate what size pipe I need? To find it, measure around the circumference of the pipe with flexible measuring tape. Divide the circumference by pi, or about 3.14159. For example, if the circumference is 12.57 inches (319 mm), you would divide by pi, and get an outside diameter of about 4 inches (100 mm). What determines pipe diameter? Measure circumference using a flexible tape and divide the outside circumference by 3.1415. Here the circumference is about 1/32″ (0.03″) less than 6″ = 5.97″. So 5.97 ÷ 3.1415 = 1.900″ diameter – 1 1/2″ nominal pipe. How can...