calcs.homes
calcs.homes
Enter the depth of the obstruction you need to clear and your bend angle to find the distance between bend marks and total shrinkage to add to your measurement.
Add shrinkage to your total conduit run length to land your last fitting in the right spot.
Each bend angle carries two constants: a multiplier (distance between bend marks = offset depth × multiplier) and a shrink factor (how much shorter the conduit gets per inch of offset). At 30°, that's a 2× multiplier and 0.25 shrink; a 45° bend uses 1.4× and 0.375. Because both figures scale directly off the offset measurement, they apply the same way whether you're working in inches or centimeters.
These multipliers come from the trigonometry of two equal-and-opposite bends, but electricians use the standard table on the job instead of recalculating trig each time — it's faster and matches what's stamped on most bender heads and cards. Shallower angles need less shrinkage added back but require a longer straight run between the two bend marks, which is the main trade-off in picking an angle.
30° is the most common choice for a standard offset — it balances a manageable bend distance against a moderate multiplier. Shallower angles (10°, 22.5°) need less shrinkage but a longer run between bends.
Because the conduit now travels at an angle instead of straight, the straight-line distance it covers is shorter than the conduit's actual length — you have to add that difference (the shrinkage) back into your overall measurement.