Pipe Cutback Calculator
Free pipe cutback and fitting takeout calculator: the length to cut back for 90 and 45 degree long and short radius elbows by NPS.
What does the Pipe Cutback Calculator do?
It returns the takeout, also called cutback, for 90 and 45 degree long radius elbows and 90 degree short radius elbows at any nominal pipe size, and the total cutback when a run has several fittings.
- Inputs: nominal pipe size, elbow type, number of fittings.
- Output: takeout per fitting and total cutback.
- Method: the standard takeout factors of 1.5, 0.625 and 1.0 times NPS.
Quick answer
A 4 inch 90 degree long radius elbow has a takeout of 6 inches. For two such fittings the total cutback is 12 inches. The factors are 1.5 x NPS for a 90 long radius elbow, 0.625 x NPS for a 45 long radius, and 1.0 x NPS for a 90 short radius.
What This Calculator Really Does
When you measure a pipe run centre to centre, the pipe you actually cut is shorter than that measurement because the fittings themselves consume some length. That consumed length is the takeout, sometimes called the cutback or the fitting allowance. For a standard long radius elbow the takeout is a simple multiple of the nominal pipe size, a rule that holds across the common sizes and saves you looking up a fitting catalogue. Getting the takeout wrong is one of the most common causes of a pipe run that comes up short or fouls an anchor, so it is worth calculating rather than guessing.
The rules it applies
- 90 degree long radius: takeout = 1.5 x nominal pipe size.
- 45 degree long radius: takeout = 0.625 x nominal pipe size.
- 90 degree short radius: takeout = 1.0 x nominal pipe size.
- Cut length: centre-to-centre distance minus the takeout for each fitting on that spool.
- Not modelled: weld gaps, the fitting wall thickness and out-of-round pipe.
Worked example with real numbers
Take 4 inch nominal pipe with 90 degree long radius elbows. The factor is 1.5, so the takeout is 1.5 x 4 = 6 inches per fitting. If a spool has two such elbows between two anchors that are 40 inches centre to centre, you subtract 2 x 6 = 12 inches and cut the pipe to 28 inches. Cut it 12 inches too long and the run will not fit; this is why the takeout is subtracted before the first cut.
Reading the result
The takeout is measured from the end of the fitting to its centreline, so the centre-to-centre length of a spool is the sum of the pipe cut length and one takeout at each end. Short radius elbows take out less length but turn more sharply, which increases pressure loss, so choose fitting type with the flow in mind as well as the geometry. On large sizes, verify the takeout against the actual fitting manufacturer data sheet before cutting, because the simple NPS factors are accurate for standard ASME B16.9 fittings but can drift on specials.
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Frequently Asked Questions
How is the pipe cutback calculated?
Multiply the nominal pipe size by the takeout factor for the fitting: 1.5 for a 90 degree long radius elbow, 0.625 for a 45 degree long radius, and 1.0 for a 90 degree short radius, then subtract that from the centre-to-centre length.
What do I need to use the Pipe Cutback Calculator?
The nominal pipe size, the elbow type and how many fittings are involved. The standard takeout factors are built in.
What does the result from the Pipe Cutback Calculator show?
The takeout per fitting and the total cutback for the run, so you know how much shorter than centre-to-centre to cut the pipe.
What is the takeout for a 90 degree long radius elbow?
One and a half times the nominal pipe size. A 4 inch 90 degree long radius elbow, for example, has a 6 inch takeout.
Is the Pipe Cutback Calculator really free?
Yes — 100 percent free, no sign-up, and everything runs in your browser.
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