Bend a 90° in a piece of conduit and something odd happens: the bent pipe is shorter than the two straight legs measured to the corner. That missing length is gain — the conduit the bend “saves” by taking the curved path instead of going all the way to the corner and back.
Picture the corner of a 90° bend. If the conduit ran straight to the corner point and then turned, it would travel the full length of both legs. The real pipe cuts the corner along an arc, and an arc is shorter than two straights. The difference — legs minus developed length — is the gain. For a 90° bend it equals about 0.4292 × the centerline bend radius, so a bigger bender radius means more gain.
Gain matters whenever you cut conduit to an exact length before bending. A stub-up that has to land at a precise height, a 90° that must hit a coupling dead on — if you cut to the corner-to-corner measurement, the finished bend comes up short by exactly the gain. On a run with several 90s the error stacks: four 90s at 1" of gain each puts you 4" off at the end of the run.
The fix is simple once you know the number: subtract the gain from your cut length. Measure twice, subtract the gain, bend once.
These three get mixed up constantly. Take-up tells you where to mark: it is the distance from the end of the pipe to the bend mark, and it is a fixed number for your bender head. Gain tells you how much shorter to cut: it is the length the bend saves. The deduct is what you actually subtract from your measurement on the job — for a 90° stub it equals the take-up. Mark with take-up, cut with gain in mind.
Multiply 0.4292 by the centerline bend radius of your bender. A head with a 6-inch radius gives about 2.6 inches of gain. Most electricians look it up once for their bender and reuse the number.
No. Take-up locates the bend mark — it is a fixed property of the bender head. Gain is the conduit length the bend saves, and it shortens your cut. Confusing the two is one of the most common bending mistakes.
Every bend has gain, because every bend cuts a corner. It matters most on 90s where the full 0.4292 × radius applies; on shallow offsets the gain is small enough that most electricians ignore it.
Gain depends on the bender's actual bend radius, and every head is slightly different. If precision matters, bend one test 90°, measure the real gain, and use your number instead of the chart's.
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