Estimates only. Check measurements, product labels and local building codes before you buy or build.
How the Pipe Cut Length Calculator works
The pipe you cut is shorter than the center-to-center measurement, because each fitting uses up part of that distance. This calculator subtracts both fitting take-outs and the gap at each joint from the center-to-center to give the cut length. A helper also gives the take-out of an elbow cut down to another angle.
Cut length = center to center − take-out A − take-out B − 2 × gap. The take-out is how much of the center-to-center a fitting uses up: center to end for a butt-weld fitting, center to the bottom of the socket for socket weld, and center to face minus the thread engagement for threaded fittings. The gap is per joint: the root gap for butt welds, the back-off for socket welds, 0 for threaded. An elbow cut to angle A has a take-out of radius × tan(A ÷ 2).
Example: 36" center to center between two butt-weld fittings with 3" take-outs and a 1/8" root gap. Cut length = 36 − 3 − 3 − 2 × 1/8 = 29 3/4".
Take-outs differ by size, schedule, fitting type and maker, so measure the fitting or use the maker's dimension sheet; the calculator never looks them up. For an offset, the center-to-center is the travel from the Pipe Offset Calculator. If the take-outs and gaps add up to more than the center-to-center, the calculator says the fittings won't fit.
Frequently asked questions
What is take-out in pipefitting?
The distance from the center of a fitting to the point where the pipe stops inside or against it. Subtracting the take-outs of both fittings from the center-to-center measurement gives the length of pipe to cut.
How do you calculate pipe cut length?
Center to center minus both take-outs minus the gaps. A threaded piece with different fittings at each end and no gap: 24 − 1 3/8 − 7/8 = 21 3/4".
What gap do I leave for a socket weld?
About 1/16" (1.5 mm) between the pipe end and the bottom of the socket before welding, so the joint is not welded bottomed out; ASME B31.1 and B31.3 show this gap. Enter it as the gap per joint, and follow the welding procedure for your job.
What is the take-out of an elbow cut to 45 or 60 degrees?
Radius × tan(angle ÷ 2). With a 3" centerline radius, a 45° cut gives 3 × 0.414 = 1.24" (1 1/4"), a 60° cut 3 × 0.577 = 1.73" (1 3/4"), and the full 90° gives the radius, 3".