Square Elbow Surface Area Calculation

Do you mean a 90° mitre bend in circular pipe? (as top right one in JohnDG's post #1) If so, it's just the area of a pipe same diameter, length = length of joint, measured along the pipe. Not easy to describe, but I'm sure you know what I mean. That's the part where the joint is, the cylindrical parts are easy to calculate.

You can see this by imagining the joint rotating 180°, when it becomes a straight pipe. If it's not a 90° bend, area is still the length measured to the midpoint of the joint x the pipe circumference x 2 for the other half of the fitting.

Cheers...........Codey

For a mitre bend, the pipe is cut at 45deg and one of the two parts rotated about its axis 180deg relative to the other before turning 90deg and sticking back together.

If the length of the pipe when starting the cut is known, the mitre bend will be made of the same quantity of material. Follow the formula for a cylinder as though the mitred pipe were actually straight.

One might allow for the thickness of the saw cut....