Conduit Offset Bending Calculator
Multiplier = 1/sin(angle) · shrinkage per field chart · mark-to-mark spacing for 10° / 22.5° / 30° / 45° offsets
Field math for hand and mechanical benders making true offsets. Shrinkage values follow the standard per-inch-of-offset chart; multipliers are exact cosecants. Saddle bends, kicks, and stub-up take-up are covered in the tables below.
Every conduit run eventually meets a beam, a duct, a joist, or a panel KO that refuses to line up. The offset bend — two equal bends in opposite directions — is how you step over it without a fitting. The math is pure right-triangle trigonometry, but nobody wants to do trigonometry on a ladder. The calculator above does it: pick your angle, enter the offset height and the distance from the conduit end to the obstruction, and it returns the distance between bends, the shrinkage you need to add back, and the exact mark positions. Below the calculator you will find the multiplier and shrinkage charts the math is built on, the step-by-step bending procedure, take-up tables for stub-ups, and the mistakes that scrap conduit on every job site.
Pair this with our conduit fill chart (how many THHN conductors fit per trade size) and the PVC vs. EMT vs. RMC selection guide — together they cover 90% of residential and light-commercial raceway questions. Need material? Allied Tube & Conduit EMT ships from us by the bundle, and Kraloy PVC covers underground and corrosive runs.
The Offset Formula: Multipliers by Bend Angle
An offset is two identical bends. The conduit between them is the hypotenuse of a right triangle whose opposite side is your offset height. The multiplier is the cosecant of the bend angle — 1 divided by the sine. Multiply the offset height by the multiplier and you get the center-to-center distance between the two bend marks. Steeper angles need less spacing but shrink the run more and are harder to pull wire through; shallow angles are gentle on conductors but eat horizontal room.
| Bend angle | sin(angle) | Multiplier (1/sin) | Shrinkage per inch of offset | Best use |
|---|---|---|---|---|
| 10° | 0.1736 | 5.76 | 1/16" | Very gradual offsets, large conduit, long pulls |
| 22.5° | 0.3827 | 2.61 | 3/16" | Tight spots where 30° will not fit |
| 30° | 0.5000 | 2.00 | 1/4" | The field default — easy math, easy pull |
| 45° | 0.7071 | 1.41 | 3/8" | Steep offsets in very short distances |
Thirty degrees is the trade standard for a reason: the multiplier is exactly 2, so a 6-inch offset puts your marks 12 inches apart — mental math you can do with gloves on. Use 10° bends when you are bending 2-inch and larger conduit or planning a long wire pull (every degree of bend adds pulling tension), and reserve 45° for offsets that must happen within a few inches, like jumping a pipe at a panel top. Anything past 45° in an offset starts to fight you on the pull, and NEC Chapter 9, Table 1 fill percentages assume you are not abusing the raceway with excessive bend. Note the hard cap that applies everywhere: NEC 358.26 (EMT), 344.26 (RMC), and 352.26 (PVC) all limit you to 360° of total bends between pull points — that is four 90s, or a lot of offsets.
Shrinkage: Why Your Conduit Comes Up Short
When you bend an offset, the conduit no longer travels in a straight line — it detours up and over. The straight-line distance it covers shrinks. Ignore shrinkage and your conduit lands short of the box by exactly the shrinkage amount, every time, and you will swear the tape measure lied. The fix: add the shrinkage back into your measurement before you mark. The calculator above does this automatically — Mark 1 is your measured distance plus total shrinkage.
| Offset height | 10° shrink | 22.5° shrink | 30° shrink | 45° shrink |
|---|---|---|---|---|
| 2" | 1/8" | 3/8" | 1/2" | 3/4" |
| 4" | 1/4" | 3/4" | 1" | 1-1/2" |
| 6" | 3/8" | 1-1/8" | 1-1/2" | 2-1/4" |
| 8" | 1/2" | 1-1/2" | 2" | 3" |
| 10" | 5/8" | 1-7/8" | 2-1/2" | 3-3/4" |
| 12" | 3/4" | 2-1/4" | 3" | 4-1/2" |
Look at the 45° column: a 12-inch offset eats four and a half inches of conduit. That is why experienced hands reach for 30° unless the architecture forces steeper. On long rack runs — say, a row of panels on a solar racking system — that shrinkage compounds across every stick, so mark every piece from a fixed reference rather than measuring end-to-previous-bend.
Worked Examples (Check the Calculator Against These)
Example 1 — 6-inch offset at 30°, obstruction 24 inches from the end. Multiplier 2.00: marks 12 inches apart. Shrinkage: 6 × 1/4" = 1-1/2". Mark 1 = 24 + 1.5 = 25-1/2". Mark 2 = 25.5 + 12 = 37-1/2".
Example 2 — 4-inch offset at 45°, obstruction 18 inches out. Multiplier 1.41: marks 5.66 inches apart (call it 5-11/16"). Shrinkage: 4 × 3/8" = 1-1/2". Mark 1 = 19-1/2". Mark 2 ≈ 25-3/16".
Example 3 — 3-inch offset at 10°, obstruction 36 inches out. Multiplier 5.76: marks 17.28 inches apart (≈17-5/16"). Shrinkage: 3 × 1/16" = 3/16". Mark 1 = 36-3/16". Mark 2 ≈ 53-1/2".
How to Bend the Offset: Step by Step
- Measure the obstruction. Measure from the end of the conduit (or the last coupling) to the near edge of whatever you are clearing, and measure how tall the step needs to be. Height is the number that drives everything.
- Pick your angle. Default to 30°. Go shallower for big conduit or long pulls, steeper only when space demands it.
- Calculate marks. Use the calculator: Mark 1 = distance + shrinkage; Mark 2 = Mark 1 + (height × multiplier).
- Make the first bend. Conduit on the ground, firm foot pressure on the bender heel, handle at about 30° of travel per stroke. Sight down the conduit to keep the bend in plane — a dogleg (two bends out of plane) cannot be fixed in the field.
- Flip and bend the second. Rotate the conduit 180°, slide it through the bender, align Mark 2 on the arrow, and bend the same angle in the opposite direction. Lay the offset flat on the floor: both straight sections should touch.
- Test-fit before you commit the run. Hold it against the obstruction. If the height is off, adjust Mark 2 spacing, not the angle.
Stub-Up Take-Up Reference (90° Bends)
Offsets are only half of field bending. The other daily calculation is the stub-up: deduct the bender's take-up from your desired stub height, mark, align the arrow, bend to 90°. Take-up is a property of the bender shoe, not the angle math above, and it is stamped on every quality hand bender.
| Conduit trade size | Typical take-up (hand bender) | Stub formula | Min. stub (NEC radius) |
|---|---|---|---|
| 1/2" EMT | 5" | Mark = stub height − 5" | 4" radius |
| 3/4" EMT | 6" | Mark = stub height − 6" | 4-1/2" radius |
| 1" EMT | 8" | Mark = stub height − 8" | 5-3/4" radius |
| 1-1/4" EMT | 11" | Mark = stub height − 11" | 7-1/4" radius |
| 1-1/2" EMT | Use mechanical bender | Per shoe chart | 8-1/4" radius |
| 2" EMT | Use mechanical bender | Per shoe chart | 9-1/2" radius |
Example: a 24-inch stub in 3/4" EMT gets marked at 24 − 6 = 18 inches from the end. Bend, and the stub stands exactly 24 inches. Get the wrong shoe or read the star instead of the arrow and every stub in the rack comes out a different height — the classic apprentice photo.
Matching the Bender to the Raceway
| Raceway | Sizes | Bender | Field notes |
|---|---|---|---|
| EMT | 1/2"–1-1/4" | Hand bender | The everyday tool; keep the shoe clean or it galling-marks the stick |
| EMT | 1-1/2"–2" | Mechanical / hydraulic | Hand bending 2" EMT is a gym workout with a quality penalty |
| RMC / IMC | 1/2"–1" | Hand bender, one shoe size up is a myth — use the right shoe | Galvanized walls fight back; more foot pressure, slower strokes |
| PVC Schedule 40/80 | 1/2"–6" | Heat blanket or hot box, never a hand bender | Cold-bending PVC kinks it; heat to ~250°F, bend, hold until set |
One caution that saves conduit: hand benders are sized to the raceway's trade size, not its measured outside diameter. A 3/4" EMT stick measures about 0.922" OD; a 3/4" bender shoe is built for exactly that. Using a 1/2" shoe on 3/4" conduit flattens the bend, and a flattened bend is a wire-pulling bottleneck the fish tape will find at 11 p.m.
The Five Mistakes That Scrap Conduit
- Forgetting shrinkage. The number-one cause of short conduit. Add it back before you mark — the calculator's Mark 1 already includes it.
- Doglegs. The two offset bends must be perfectly in plane and exactly 180° opposed. Sight down the stick before every bend.
- Over-bending past the angle. Springback is real but small in EMT; if you consistently overshoot, bend in shorter strokes and check with the bender's angle marks or a digital level.
- Measuring Mark 2 from the wrong reference. Both marks measure from the same conduit end. Measuring Mark 2 from the first bend's center instead of the end adds the multiplier error on top of everything else.
- Stacking too much bend between pull points. Offsets count toward the NEC 360° limit. Two 45° offset bends plus two 90s is 270° — legal, but your pull tension says otherwise. Plan a pull point or conduit body on long runs.
When the raceway is bent and strapped, the next questions are fill and wire: how many conductors the run legally carries (conduit fill chart), what gauge the circuit needs (NEC ampacity chart), and which THHN to pull (Cerro, THHN by the spool). Bending gear and layout tools live in tools & test equipment, and boxes, straps, and fittings in electrical boxes & covers and electrical supplies. If the run feeds PV, the PV wire vs. USE-2 vs. THHN guide and NEC code compliance guide are the next two tabs to open. For whole-job material takeoffs, hit the quote button in the calculator — your marks travel with the request.
Frequently Asked Questions
What is the multiplier for a 30-degree offset?
Exactly 2.0. Multiply the offset height by 2 to get the distance between bend marks. A 5-inch offset needs marks 10 inches apart. The 30° bend is the field standard precisely because this math is trivial.
How much does conduit shrink in an offset?
Per inch of offset height: 1/16" at 10°, 3/16" at 22.5°, 1/4" at 30°, and 3/8" at 45°. Multiply by your offset height and add the result to your measured distance before placing Mark 1 — that single habit eliminates short-conduit callbacks.
Why does my offset come out crooked even when the measurements are right?
That is a dogleg: the two bends are not in the same plane. It comes from rotating the conduit more or less than 180° between bends, or from the conduit rolling in the bender. Sight down the stick before the second bend and keep firm heel pressure to stop rotation.
Can I bend PVC conduit with a hand bender?
No. PVC must be heated — with a heat blanket, hot box, or heat gun kept moving — until pliable (about 250°F), then bent around a form and held until it sets. A hand bender on cold PVC kinks the wall and ruins the stick.
How many bends are allowed between pull points?
NEC caps total bends at 360° between pull points (junction boxes, conduit bodies, panel entries) for EMT (358.26), RMC (344.26), and PVC (352.26). Offset bends count at full value. Long runs with multiple offsets should include a pull point to keep wire tension manageable.
What angle should I use for large conduit offsets?
Go shallow: 10° or 22.5° for 1-1/2" EMT and up. Large conduit kinks at steep hand-bend angles, and the gentle slope dramatically reduces pulling tension. Accept the longer mark spacing — the multiplier at 10° is 5.76, so plan the run layout accordingly.
