Conduit Offset Calculator
By Andrew ·
Quick answer
An offset calculator turns a height and an angle into two marks and a shrink. Distance between bends = height × multiplier, the multiplier being 1 ÷ sin of the angle; shrink = height × shrink per inch. At 30° the multiplier is 2 and shrink is about 1/4" per inch, so a 6" offset has marks 12" apart and takes about 1 5/8" off the run.
Calculator
- Results
- Distance between bends
- 8"
- Shrink
- 1 1/16" (1.07")
Worked out the textbook way, from the bend angle alone. BendMate also uses your bender’s radius, deduct and shoe.
The two formulas behind every offset
Both bends of an offset are bent to the same angle, so the conduit climbs along a slanted line and the marks sit at the two ends of it. That slanted line is the hypotenuse of a right triangle whose short side is your offset height.
between bends = height × multipliershrink = height × shrink per inchMeasure the height from center of conduit to center of conduit. Measuring the bottom of the pipe before the offset and the bottom after it gives the same number.
Worked example: a 6" offset at 30°
- Offset height
- 6"
- Angle
- 30°
- Multiplier
- 2.000
- Distance between bends
- 6" × 2.000 = 12"
- Shrink
- 6" × 0.268 = about 1 5/8"
- Make the first mark where the offset should begin.
- Make the second mark 12" further along the conduit.
- Bend the first mark to 30°, roll the conduit half a turn, then bend the second mark to 30°.
- Add the shrink (about 1 5/8") to the length you cut if the run has to land on an exact dimension.
Which angle to pick
| Angle | Multiplier | Shrink per inch | Marks apart |
|---|---|---|---|
| 10° | 5.759 | 0.087 | 34 9/16" |
| 15° | 3.864 | 0.132 | 23 3/16" |
| 22.5° | 2.613 | 0.199 | 15 11/16" |
| 30° | 2.000 | 0.268 | 12" |
| 45° | 1.414 | 0.414 | 8 1/2" |
| 60° | 1.155 | 0.577 | 6 15/16" |
30° is the default: short enough to fit most spots and gentle enough to pull wire through. Go to 45° or 60° when the space is tight and the offset is tall, and accept the extra shrink. 10° and 15° make long, easy offsets, but the marks spread out fast.
Mistakes that make an offset come out wrong
- Bending the two bends to different angles, which leaves the far end pointing off the original line.
- Forgetting to turn the conduit half a turn between bends, which gives a dogleg instead of an offset.
- Using the shrink of one angle with the marks of another.
- Measuring the offset height to the edge of the conduit at one end and the center at the other.
How it relates to your bender
The multiplier method treats each bend as a sharp corner. A real shoe bends on a radius and uses a little less conduit, so on a hand bender the exact marks come out a touch under 12" for this offset. In BendMate the same math accounts for your bender's radius and deduct.
Get the marks for your bender
BendMate works this out from your bender’s radius and deduct, flags a bend that won’t work, and shows you every mark.
Common questions
How do you calculate a conduit offset?
Multiply the offset height by the multiplier for your angle to get the distance between the two bends, and multiply it by the shrink per inch to find how much shorter the conduit gets. Bend both marks to the same angle, turning the conduit half a turn in between.
What is the multiplier for a 30 degree offset?
It is 2.000, which the trade rounds to 2. A 4" offset at 30° has the bend marks 8" apart.
How much does an offset shrink the conduit?
Shrink = height × tan(angle ÷ 2). At 30° that is 0.268" per inch of offset, about 1/4" in the shop rule, and at 45° it is 0.414" per inch, about 3/8".
Does the offset calculator work for EMT, rigid and PVC?
The marks and shrink come from geometry, so they hold for EMT, rigid and IMC alike; only the bender changes the real marks slightly. PVC is bent with heat rather than a shoe, but the offset triangle is the same.