Offset & saddle shrink calculator

Conduit bending lookup: deducts, offset marks, saddle shrink, and tape fractions

Four numbers get re-derived at every bender: the take-up stamped on your hook, the marks for the offset you are cutting, the shrink to add back before the first bend, and the fraction a decimal result rounds to on the tape. The tables here hold the values that do not change with the job, so the only variable left is the rise you measured.

Bender take-up by conduit size

Take-up (also called deduct) is the fixed distance between the bender’s arrow and the finished bend. It depends on the bender and the conduit size, never on the angle, and it shifts where marks land on the pipe rather than how much pipe the run needs.

These are the common hand-bender figures for EMT; rigid and IMC benders run different values, and the number cast into your own bender’s hook wins over any table. Verify against the stamp before a full day of stub-ups. The same deduct also sets the back-of-90 and the start of a stub, so it is worth confirming once and trusting all day.

Offset marks and shrink at a glance

Mark spacing is the distance between the two bend marks, equal to rise times the angle multiplier. Shrink is rise times the shrink-per-inch constant, rounded to the nearest 1/16" for the tape. Both scale linearly with the rise, so a value not listed interpolates cleanly.

Multipliers used above are 2.000 at 30° and 1.414 at 45°; shrink-per-inch is 0.2679 and 0.4142. The 30° column stays mental because sin 30° is exactly 0.5, so the marks are always twice the rise.

Three-point saddle quick reference

A 3-point saddle is two offset bends sharing one center bend, so the mark multiplier is unchanged but the shrink doubles. The center mark lands at the midpoint of the obstruction; each side mark sits at obstruction-width/2 plus rise/sin θ, measured out from that center.

A saddle over another conduit uses that pipe’s outside diameter plus clearance as the rise, so a run crossing a 3/4" EMT (about 0.92" outside diameter) with a half-inch of gap takes roughly a 1 3/8" rise.

Decimal inch to nearest 1/16"

The calculator carries full float precision, but a tape reads to 1/16". Round any decimal result to the nearest sixteenth using this conversion; a shrink of 1.607", for instance, reads as 1 5/8" because .607 is nearest .625.

Related concepts

• Take-up vs shrink: take-up moves where marks land; shrink changes how much pipe you feed. Counting one as the other is the classic short-run mistake.
• Gain: the length a 90° bend saves against a squared corner, take-up’s cousin for stub-ups.
• Rolling offset: an offset in two planes at once, solved with the same angle constants applied to the true diagonal between boxes.
• Four-point saddle: for obstructions too wide for a center bend, run as two offsets facing each other.
• Concentric bends: large-radius sweeps for parallel runs, split into many small kicks with a growing radius per pipe.