There is a moment, the first time you bend an offset, when the conduit comes out of the bender looking exactly right and lands two inches short of the box. It looks right because the angles are right. It lands short because nobody told you the pipe gets shorter when you bend it. That single fact — that an offset eats length — is the difference between a piece you install and a piece you cut up for shorts.
So let us walk through a real offset slowly, the way you would teach an apprentice on the truck, and put numbers to every step.
What an offset is actually doing
An offset is two equal bends in opposite directions that step the conduit up (or over) by some amount and then run parallel again. You use it to jog a pipe from a stud bay onto the face of a box, to come off a wall and into a panel, to clear an obstruction. The two things you need to control are the rise — how far the pipe steps over, which electricians call the depth of the offset — and the distance between the two bends, which sets that depth.
Everything in offset bending comes down to one relationship: the steeper the bend angle, the closer together the two bends sit for the same depth. A shallow 10-degree offset needs the marks far apart. A sharp 60-degree offset needs them close. The number that converts the depth you want into the distance between marks is the multiplier.
The multiplier
The multiplier is the cosecant of the bend angle, but you do not need the trigonometry on the job. You need five numbers committed to memory, because they cover almost everything you will ever bend:
- 10 degrees: multiplier of 6.0
- 22.5 degrees: multiplier of 2.6
- 30 degrees: multiplier of 2.0
- 45 degrees: multiplier of 1.4
- 60 degrees: multiplier of 1.2
The rule is simple. Distance between bends = offset depth × multiplier. Want a 5-inch offset using 30-degree bends? Five inches times two is ten. Your two marks go ten inches apart. Bend the first mark to 30 degrees, slide the pipe, rotate it 180 degrees so the second bend goes the opposite way, and bring the second mark to 30 degrees. Lay it on the floor and the rise should measure five inches.
Why is 30 degrees the workhorse? Because the multiplier is a clean 2 — the mental math is instant — and because a 30-degree offset is shallow enough to feed conductors through without scuffing insulation but sharp enough to keep the marks a reasonable distance apart. Most electricians default to 30 unless something forces a different angle: tight space pushes you toward 45 or 60, a long gentle transition pulls you toward 10 or 22.5.
Shrink — the part that gets people
Here is the fact that lands the offset short. When you bend the conduit up and over, the diagonal path between the two bends is longer than the straight horizontal run it replaced. The conduit has to "spend" length climbing the offset. That lost horizontal length is shrink, and if you do not account for it, your end-of-pipe measurement walks backward.
Shrink scales with the depth of the offset and with the angle. The published per-inch values most benders use are:
- 22.5 degrees: about 3/16 inch of shrink per inch of depth
- 30 degrees: about 1/4 inch per inch of depth
- 45 degrees: about 3/8 inch per inch of depth
- 60 degrees: about 1/2 inch per inch of depth
Take that 5-inch, 30-degree offset. Shrink is a quarter inch per inch of depth, so five inches of depth costs you 1-1/4 inches of overall length. If your stub needs to be 12 inches from the end of the pipe to the center of the first bend, you do not measure 12 inches — you measure 12 plus 1-1/4, or 13-1/4 inches, before you make the first mark. Skip that, and the pipe lands an inch and a quarter short every time, no matter how perfect your angles are.
Putting it together, one pipe
Say you are coming off a box and need to drop the pipe down 4 inches to clear a beam, then continue. You decide on 30-degree bends.
- Distance between bends: 4 inches of depth × 2.0 = 8 inches between your two marks.
- Shrink: 4 inches × 1/4 = 1 inch lost. Add it to your end measurement so the finished length comes out right.
- Mark one, bend to 30 degrees with the arrow on the bender lined up to your mark. Reading the bender's degree marks or a magnetic level here matters more than people admit — five degrees off doubles up across both bends.
- Rotate 180 degrees, mark two, bend again to 30 degrees in the opposite direction.
- Check on the floor. A finished offset should lie flat — both straight legs touching the ground. If the pipe rocks, your two bends are not in the same plane; you twisted the conduit between bends. That is the second most common offset failure after shrink, and the fix is to always keep the same reference line (a Sharpie stripe down the pipe) facing up through both bends.
Where the trade lore ends and the code begins
Bending is craft, but it lives inside rules. The NEC limits the total bends between pull points to the equivalent of four quarter bends — 360 degrees — in one run (Chapter 3, the raceway articles), because every degree of bend adds pulling tension and risks damaging conductor insulation. Two offsets and a 90 add up faster than you would think. And conductors have a minimum bend radius; a too-tight offset on a large pipe can kink the raceway or scrape insulation on the pull. None of this replaces reading the conduit article that applies to your raceway type and verifying it against the edition of the code your jurisdiction has adopted, alongside a licensed electrician's judgment. The math gives you a clean pipe; the code keeps it legal and safe.
Letting the numbers ride along
The reason offsets get botched is rarely the trade knowledge — it is doing the arithmetic in your head on a cold morning while holding a bender. Multiplier times depth, plus shrink, while someone asks you a question. That is exactly the kind of error Voltly is built to take off your plate. Its conduit-bending tool lets you pick the angle, punch in the depth, and read back the distance between bends, the multiplier, and the shrink — with a clean labeled diagram of the bend so you can see what you are about to make before you make it. It remembers your last conduit size and angle, and it works with no signal in a basement or a steel building, because it is fully offline. If you would rather spend your morning installing pipe than recovering from a short cut, Voltly is worth a look.