An offset is two equal, opposite bends that shift a conduit or pipe sideways by some height while it keeps traveling forward; between the bends the tube runs along the hypotenuse of a right triangle whose opposite side is that rise. The distance between the bend marks is therefore exactly height ÷ sin(angle), and the offset multiplier is that identity compressed into a memorized constant: 1/sin(10°) = 5.76, 1/sin(22.5°) = 2.613, 1/sin(30°) = 2.000 exactly, 1/sin(45°) = 1.414, 1/sin(60°) = 1.15. The trade multipliers are cosecants rounded for field use — nothing more mystical than that — and pipefitters use the identical numbers for fitting travel, where travel = offset × 1/sin(angle).
The multiplier table doubles as a decision table. A shallow 10° offset spreads its bends 5.76 rises apart — gentle on the wire pull, stingy with shrink, greedy for room; a steep 60° fits where nothing else will but costs pulling friction and shortens the run the most. The 30° bend is the trade default for an honest reason: its multiplier is exactly 2, turning layout into doubling the rise in your head, in the comfortable middle of the space-versus-pull compromise. The companion number on every layout is the shrink, h·tan(a/2) — how much the run gets shorter because the tube now travels the hypotenuse — added to the obstruction measurement before the first mark goes down.