About Conduit Bending Calculator (Offset, Saddle, Stub-Up)
The conduit bending calculator lays out the marks for the three bends every electrician makes with a hand bender: the two-bend offset, the 3-point saddle, and the 90 degree stub-up. For an offset it computes the exact distance between bends as height / sin(angle) — the familiar trade multipliers 5.76, 2.61, 2.0, 1.41, and 1.15 for 10, 22.5, 30, 45, and 60 degrees are just this value rounded — along with the shrink, the amount the conduit run gets shorter because it travels the hypotenuse instead of the straight line.
For a 3-point saddle the tool treats the bend as two back-to-back offsets at half the center angle, giving the distance from the center mark to the two outer marks and the shrink to add to the center measurement. For a 90 degree stub-up it subtracts the bender take-up deduct for the EMT trade size (5 in for 1/2", 6 in for 3/4", 8 in for 1", 11 in for 1-1/4") from the stub height to place the bend mark, and supports back-to-back 90s measured outside to outside. Enter distances in inches or millimetres.
How It Works
- Pick the bend type: offset, 3-point saddle, or 90 degree stub-up, and choose inch or millimetre units.
- Offset: enter the offset height and bend angle (standard 10, 22.5, 30, 45, 60 degrees or a custom 5-60 degree angle). The tool returns the distance between bends, the shrink, and — given the distance to the obstruction — both bend mark positions.
- Saddle: enter the obstruction depth and choose a 45 degree center bend (two 22.5 degree returns) or 60 degree center (two 30 degree returns). The tool returns the center-mark shrink and the spacing to the two outer marks.
- Stub-up: enter the desired stub height and EMT trade size; the mark from the conduit end is the height minus the bender take-up. Add a back-to-back distance to lay out a second 90 measured outside to outside.
- If you supply the conduit OD, the tool warns when the distance between offset bends is less than twice the OD, where the bends would overlap on the bender shoe.
Worked Example
A 1/2" EMT run must rise 6 in to clear a beam, with the beam edge 60 in from the conduit end, bent as a 30 degree offset. The multiplier is 1/sin(30 deg) = 2.0, so the distance between bends is 6 x 2.0 = 12.0 in. The shrink is 6 x (1 - cos 30)/sin 30 = 6 x 0.268 = 1.61 in, so the first mark goes at 60 + 1.61 = 61.61 in and the second at 61.61 + 12.0 = 73.61 in. Had the same run needed a 12 in stub-up instead, the 1/2" EMT take-up of 5 in puts the bend mark at 12 - 5 = 7 in from the end.
Formulas
- Offset distance between bends
D = h / sin(a) = h * multiplier- Offset shrink
shrink = h * (1 - cos a) / sin a = h * tan(a / 2)- 3-point saddle marks
outer mark spacing = d / sin(a_c / 2); shrink = d * tan(a_c / 4)- 90 degree stub-up mark
mark = stub height - take-up
Standards & References
- NEC Chapter 9 Table 2 -- conduit bend radius requirements
- NEC 358.24 / 344.24 -- bends in EMT and RMC (no more than 360 degrees between pull points, NEC 358.26)
- UL 797 -- electrical metallic tubing
Frequently Asked Questions
Where do the offset multipliers 5.76, 2.61, 2.0, 1.41, and 1.15 come from?
They are the cosecant of the bend angle, 1/sin(a), rounded for field use. The offset height and the run between bends form a right triangle where the conduit is the hypotenuse, so the distance between bends is height divided by sin(angle). For example 1/sin(30 deg) = 2.000 exactly, 1/sin(45 deg) = 1.414 which the trade rounds to 1.41, and 1/sin(22.5 deg) = 2.613 rounded to 2.61.
What is conduit shrink and why do I add it to my measurement?
When an offset is bent, the conduit travels the hypotenuse of the offset triangle instead of the straight line, so the run ends up shorter — that loss is the shrink, equal to height x (1 - cos a)/sin a, or height x tan(a/2). Practically you add the shrink to the measured distance before placing the first mark so the finished offset lands exactly at the obstruction. At 30 degrees the shrink is about 1/4 in per inch of rise (exactly 0.268), and at 45 degrees about 3/8 in per inch (0.414).
How do I lay out a 3-point saddle?
Measure to the center of the obstruction, add the shrink, and place the center mark there; then place the two outer marks at depth x 2.61 either side for a 45 degree saddle (or depth x 2.0 for a 60 degree saddle). The center bend is made first at 45 (or 60) degrees, then the conduit is flipped and the two return bends are made at half that angle, 22.5 (or 30) degrees. The trade shrink rule of 3/16 in per inch of depth for a 45 degree saddle is the exact half-angle value (1 - cos 22.5)/sin 22.5 = 0.199 rounded down.
What is bender take-up and why is it different for each EMT size?
Take-up (also called the deduct) is the length of conduit consumed by the curved section of a 90 degree bend, set by the bender shoe radius. Larger conduit requires a larger bend radius per NEC Chapter 9 Table 2, so the take-up grows with trade size: 5 in for 1/2" EMT, 6 in for 3/4", 8 in for 1", and 11 in for 1-1/4". To hit a stub height, subtract the take-up from the height and align that mark with the arrow on the bender.
How do I bend back-to-back 90s?
Bend the first 90 normally using the take-up deduct. Then measure from the BACK (outside) of that 90 to where the back of the second 90 must land — the outside-to-outside distance — and place a mark there. The second bend is made in the opposite direction with the mark aligned to the star point (back-of-90 reference) on the bender rather than the arrow, so no take-up deduction is needed for the second mark.
Which offset angle should I use?
Shallow angles (10-22.5 degrees) pull easier because the wire sees gentler direction changes, and they shrink less, but they need much more room: a 10 degree offset spreads the bends 5.76x the rise apart. Steep angles (45-60 degrees) fit tight spaces but shrink more and add pulling friction. Most electricians default to 30 degrees because the multiplier is exactly 2 — easy mental math — and it balances space against pull effort. The calculator warns when the chosen angle puts the bends closer together than twice the conduit OD, which is impractical to bend cleanly.