How to Find Elbow Center of Pipe?

  If the elbows in your pneumatic conveying system need to be replaced due to wear or abrasion or if you’re designing a new layout for your system, correctly measuring your existing elbows to ensure you order the right size is key.


For standard degrees of pipe elbows such as 45° pipe elbows and 90°pipe elbows, elbow center to end dimensions are available in standard pipe charts. But many times, custom elbow angles are required at site which should be cut from standard 45° or 90° elbows.


The formula for calculating the center to end distance of such elbows is as follows: Elbow length in mm = Tan(Elbow Angle/2)Elbow Radius in mm


For 90° Long Radius elbows, the center to end dimension given in dimension tables of ASME B16.9 is the same as the radius of the elbow. This is because Tan(90/2) i.e. Tan 45 is 1. Normally custom elbow angles from 45 degree to 90 are cut from 90 degrees standard elbow. But for custom elbow angles smaller than 45 degree, the elbow is normally cut from the existing standard 45-degree elbow. Center to end dimension given in dimension tables for 45-degree elbow must be divided by Tan(22.5) to get the elbow radius for a standard 45-degree elbow. Then we can use the above formula to get elbow angle for custom degrees.


45 Degree Elbow,45 degree pipe bend



Calculate Elbow Center Example :

Calculate elbow center to end dimension for 2 inch nominal pipe diameter elbow at 30 degree angle, cut from 45 degree LR elbow.

From ASME B16.9, the center to elbow dimension for 2 inch 45 degree elbow is 35 mm.

Radius of elbow = 35/Tan(22.5)

Radius of elbow = 35/0.4142 = 84.5 mm

Length = 0.26795 X 84.5= 22.64 i.e. 23 mm Approx.


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