The deduct is the number you subtract from your measurement to find where to put the bend mark. It is the most practical of the three bending numbers: the multiplier tells you spacing, shrink tells you what the bend eats, and deduct tells you where to draw the line.
For a 90° stub-up, the deduct is the take-up — the fixed number for your bender head. The classic example every apprentice learns: 1/2" EMT in a standard hand bender has a 5" take-up. Want a 30" stub? Subtract 5", mark at 25", put the bender's arrow on the mark, and bend to 90°. The stub comes out at 30".
Forget the deduct and the stub lands 5" too tall — exactly the take-up you failed to subtract. There is no partial credit in stub heights.
Take-up is stamped on most bender heads or printed in the manufacturer's chart, listed by conduit size. It is an empirical number — measured from the actual head, not derived from a formula — so use the number for your bender, not a generic table. Two heads for the same size EMT can differ.
On offsets, the “deduct” idea is replaced by shrink: you do not subtract a fixed number, you add the shrink back to your cut length. On saddles, you lay out from the centerline of the obstruction instead of deducting. The deduct rule — subtract take-up, mark, bend — belongs to 90s.
For 90-degree stub-ups, yes — the deduct is the take-up. For offsets, use shrink instead of a deduct; for saddles, lay out from the obstruction's centerline.
Most hand benders stamp it on the head near the size markings, or print it in the manufacturer's bending chart. If yours is worn off, bend a test 90° and measure — take-up is the distance from the pipe end to the arrow mark.
The stub comes out too tall by exactly the deduct — 5 inches too tall on 1/2-inch EMT with a standard bender. Cut a new piece; you cannot unbend the extra height.
No. Saddles are laid out from the center of the obstruction with the center bend first, then the side bends. Deduct is a 90-degree-stub concept.
Try it free: Open the free stub-up calculator — all six bend calculators, no sign-up.
Get Conduit Bend Calc on Google Play for bender calibration and Pro tools.