Pipe Elbow Calculator
Determine exact center-to-face takeout dimensions, cut-back allowances, and weld gap adjustments for butt-weld pipe fittings.
Takeout = Radius × tan(θ / 2). For a standard 90° LR elbow, tan(45°) = 1.0, making takeout simply 1.5 × NPS.
Buttweld Pipe Elbow Takeout Formulas
In pipefitting, "takeout" is the distance from the intersection center point of the two pipe centerlines to the weld bevel face of the fitting:
- 90° Long Radius (LR):
Center-to-Face = 1.5 × NPS(e.g. 4" NPS = 6.0" takeout) - 90° Short Radius (SR):
Center-to-Face = 1.0 × NPS(e.g. 4" NPS = 4.0" takeout) - 45° Long Radius:
Center-to-Face = 1.5 × NPS × tan(22.5°) = 1.5 × NPS × 0.4142 = 0.6213 × NPS(or 5/8" per inch of NPS)
Frequently Asked Questions
What is the takeout for a 45° LR elbow?
The formula is 1.5 × NPS × 0.4142. A fast mental rule of thumb is 5/8" per inch of nominal pipe size (e.g. 2" pipe = 1-1/4" takeout).
When are Short Radius (SR) elbows used?
Short radius elbows (1.0D) are used strictly in tight quarters and skid-mounted packaging where clearance is limited, but cause higher friction pressure drop.
Why must root gap be deducted?
Buttweld joints require a 3/32" to 1/8" root gap between pipe and fitting for full-penetration welding. Subtracting the gap from pipe cut length ensures center-to-center dimensions remain exact.