Cutting pipe to fit between fittings
The pipe you cut is shorter than the distance it spans, because each fitting swallows some length and then gives a little back where the pipe screws or sockets in. Pipefitters call the net amount the take-out. Measure the run center to center, subtract each fittings take-out, add back the engagement, and you have the exact cut length — no trial fitting.
The formula
Cut length = center-to-center distance – (take-out A – engagement A) – (take-out B – engagement B). Take-out is the distance from a fittings center to its face; engagement is how far the pipe seats into it (thread make-up for screwed pipe, socket depth for socket-weld or copper).
Typical 90-degree elbow take-outs
| Pipe size | Threaded elbow take-out (in) |
|---|---|
| 1/2 in | about 1.1 |
| 3/4 in | about 1.3 |
| 1 in | about 1.5 |
| 1-1/2 in | about 2.0 |
Use the manufacturer take-out for your fittings where you can; socket-weld and copper sweat fittings differ from threaded.
Related pipe tools
For the capacity of the run, see the pipe volume calculator; for area to coat or insulate, the pipe surface area calculator.
Worked example
A 24 in center-to-center run with two threaded elbows, each 1.125 in take-out and 0.5 in thread engagement: cut = 24 – (1.125 – 0.5) – (1.125 – 0.5) = 22.75 in.
FAQ
Center-to-center or end-to-end?
This uses center-to-center, the most common layout dimension. If you have face-to-face, the fitting faces are already accounted for, so subtract only the engagement, not the full take-out.
Why add engagement back?
Because the pipe end runs past the fitting face into the threads or socket. That buried length is real pipe you must cut, so it gets added back after the take-out is removed.