Use the free Conduit Bend Offset Calculator below. It runs entirely in your browser, with no sign-up and no download.
Two bends and a problem
An offset bend is one of the most common bends in electrical work, and one of the easiest to get wrong. You need the conduit to step sideways, usually to enter a box or clear an obstruction, and then run parallel to where it started. That takes two bends in opposite directions. The hard part is not making the bends. It is knowing where to mark them, because the conduit shortens along its original direction as the offset rises. Electricians call that loss shrink, and if you ignore it, your second bend lands in the wrong place and the run misses its box.
This calculator gives you the three numbers an offset bend needs: the travel distance between the two bend marks, the total shrink, and the adjacent distance along the original line. Enter the offset depth and the bend angle, and it works them out from plain trigonometry. It is an educational estimator for hand benders, and it is worth proving the first bend on scrap conduit before you bend the piece that matters.
The geometry in plain terms
Picture the offset as a right triangle. The offset depth is one side, the travel between bends is the hypotenuse, and the adjacent distance is the side along the original direction. The bend angle is the angle between the original direction and the offset leg. Travel equals depth divided by the sine of the angle. Adjacent equals depth divided by the tangent of the angle. Shrink is the difference between travel and adjacent, the length the run loses along its original direction.
That is why electricians memorise multipliers. For a 30 degree bend, the multiplier is 2, because one divided by the sine of 30 degrees is 2, so a 6 inch offset needs 12 inches between bend marks. For 45 degrees the multiplier is 1.414. For 22.5 degrees it is 2.613. The calculator removes the need to remember them, but knowing that the multiplier is just cosecant of the angle helps you spot a wrong answer instantly.
A worked example
Suppose a conduit must offset 6 inches to enter a panel, using 30 degree bends, with the first bend mark 12 inches from the end of the conduit. Travel is 6 divided by the sine of 30 degrees, which is 12 inches, so the second bend mark goes at 24 inches from the end. Shrink is travel minus adjacent, where adjacent is 6 divided by the tangent of 30 degrees, about 10.39 inches, so shrink is about 1.61 inches. That means the run ends up 1.61 inches shorter along its original direction than it would have without the offset, and any box position or coupling measured from the far end must allow for it.
If you used 45 degree bends instead, travel would be 8.49 inches and shrink 2.49 inches. Steeper bends save space between marks but cost more shrink and put more stress on the conduit and the wire pulled through it. Shallower bends, like 22.5 degrees, need much more room between marks, 15.68 inches for the same 6 inch offset, but shrink only 1.47 inches and pull wire more easily.
Bending technique that protects the numbers
Good numbers still need good bends. Mark both bend points before bending either one, and mark which side of each mark the bend starts on, because bending on the wrong side of a mark shifts the whole offset. Keep both bends in the same plane, or the offset will dogleg sideways as well as up. Bend a little, check against a square, and sneak up on the angle rather than bending past it and trying to come back, which kinks thin wall conduit.
After bending, check the offset against the obstruction or box it must clear, and check that the conduit still runs parallel after the second bend. A second bend a degree or two off leaves the run drifting sideways for its whole remaining length, which is far harder to fix than a single bend that is slightly over or under angle.
Frequently asked questions
What angle should I choose? Thirty degrees is the usual compromise for hand benders: easy to bend, moderate shrink, and a multiplier of 2 that is simple to remember. Use 45 degrees where space is tight and 22.5 degrees where wire pulling ease matters most.
Does conduit size change the maths? No. The triangle is the same at any size. What changes is the bend radius and the minimum bend radius the code allows, which grows with conduit size and with the wire inside it.
Why does my offset not match the calculator? The usual causes are bending on the wrong side of a mark, springback in the conduit, and measuring the offset to the wrong face. Bend a test piece, measure what you actually got, and adjust your marks by the difference.
Spanish version
Calculadora de Curvas Desplazadas en Tubo – Desplazamiento, Contracción y Distancia