Calculate the outer diameter of the pipe to the fourth power. For example, if the outer diameter equals 2 inches, then the diameter raised to the fourth power, or 2^4, equals 16.
Calculate the inner diameter of the pipe to the fourth power. For example, if the inner diameter equals 1 inch, then the diameter raised to the fourth power, or 1^4, equals 1.
Subtract the outer diameter to the fourth power by the inner diameter of the fourth power. For the example, 16 subtracted by 1 equals 15.
Multiply that number by π. For the example, 15 multiplied by π equals 47.124.
Divide that number by the outer diameter multiplied by 32. For the example, the outer diameter multiplied by 32 equals 64. Dividing 47.124 by 64 results in 0.763. The section modulus of the pipe is 0.763.