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Long radius vs short radius elbow: what LR and SR change in your calculations

A long-radius (LR) 90° elbow has a bend radius of 1.5 × NPS; a short-radius (SR) elbow has a radius of 1.0 × NPS. On a 4" ell that is 6" of radius against 4", and it changes every takeout, offset and odd-angle cut that fitting is part of. FitterMaster asks for Series on every screen that uses an elbow so the radius is always right.

2 min read · Updated 2026-09-15

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What actually differs between LR and SR?

Only the bend radius. Long radius, the more common stock elbow, bends on a radius of 1.5 × NPS. Short radius bends tighter, on a radius of 1.0 × NPS, for jobs where there is not enough room for the wider LR sweep. Stock gets mixed up easily on tight jobs, which is why Series sits right next to Size on every screen that needs it. Short-radius 90° elbows are made from NPS 1 up; there is no SR below that.

A smaller radius means a shorter center-to-face on every angle, not just 90°, because the whole elbow is a smaller circle.

Where do you pick Series in FitterMaster?

  1. In Offset, under Fitting, the Series control is LR or SR, right next to Size.
  2. In Odd-Angle Cut (Pro), under Elbow, pick Series before you set the Cut Angle θ.
  3. In Dummy Leg (Pro), when Coped onto is set to 90° LR elbow (back), pick the elbow's Series too.

LR vs SR side by side, 4" elbow

Odd-Angle Cut, 4" elbow, LR (R = 6") vs SR (R = 4")
Cut Angle θLR New Center-to-FaceSR New Center-to-Face
22.5°1-3/16"0-13/16"
30°1-5/8"1-1/16"
45°2-1/2"1-11/16"
60°3-7/16"2-5/16"

At 90° the two simply read their own radius: 6" for the LR ell, 4" for the SR ell.

Does Series change the Offset takeout too?

Yes. At 90° and at 45° long radius, Offset looks up the published B16.9 takeout table. At every other angle — including 45° short radius — it uses the same geometry as Odd-Angle Cut: radius × tan(angle ÷ 2), with the LR or SR radius you picked. Get the Series wrong on a rolling offset and the Cut Length comes out short or long by the difference between the two radii.

Questions and answers

What is the radius of a long radius elbow?
1.5 × the nominal pipe size. A 6" LR elbow has a 9" bend radius.
What is the radius of a short radius elbow?
1.0 × the nominal pipe size, so a 6" SR elbow has a 6" bend radius, two-thirds of the LR radius at the same size.
Do SR elbows come in every size?
In FitterMaster's tables, short-radius 90° elbows start at NPS 1; there is no SR option below that size.
Does the Series setting affect the offset multiplier?
No, the multiplier (1 ÷ sin of the fitting angle) only depends on the angle. Series changes the takeout that gets subtracted from the travel, not the multiplier itself.

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