The multipliers are all 1/sin θ

When to use this: laying out an offset around an obstruction, saddling over a pipe, or working out where to mark a 90° stub.

Every bender is stamped with the same five numbers — 6 for 10°, 2.6 for 22.5°, 2 for 30°, 1.4 for 45°, 1.2 for 60°. They look like a lookup table to be memorised. They are 1/sin θ, rounded for mental arithmetic.

Knowing that is the difference between bending the five angles the tool is marked for and bending any angle you can measure — which matters when a fixed obstruction dictates the geometry rather than the bender does.

The 37° and 15° rows have no chart value because no bender is marked for them. They work exactly the same way.

Shrink is the number that gets forgotten

Put an offset in a run and the conduit travels a diagonal instead of a straight line, so the far end pulls back toward you. That is shrink, and it is tan(θ/2) per unit of offset depth.

It is small per bend and it accumulates. Three 6″ offsets at 30° in one run lose 4 13/16″ between them — comfortably enough to leave the conduit short of the box after every individual measurement was taken correctly.

The traditional pocket chart rounds these down — 3/16″ for 22.5°, 1/4″ for 30°, 3/8″ for 45° — so a run bent to chart figures finishes fractionally short every single time. The exact values are 0.199, 0.268 and 0.414.

Choosing the angle is a trade

A shallow bend spaces the marks far apart and barely shortens the run, and it is much kinder to a wire pull — every degree of bend multiplies the tension needed. A steep bend fits the offset into a short length and costs you both.

30° is the usual default for one reason: its multiplier is exactly 2, so the arithmetic works in your head on a ladder.

Three-point saddles

Going over an obstruction rather than around it. A 45° bend at the centre with 22.5° bends either side, in the opposite direction.

1. Mark the centre of the obstruction on the conduit.
2. Mark 2.5 × the saddle depth on each side of that mark.
3. Bend the centre mark first, 45°.
4. Bend the two outer marks at 22.5°, opposite to the centre bend.

Shrink is about 3/16″ per inch of depth. The 2.5 multiplier is specific to this 45°/22.5° combination and is not 1/sin 45° — the geometry involves all three bends, not one.

90° stubs and take-up

Take-up is the distance from the end of the conduit to the mark, subtracted from the stub height. It is a property of the bender, not the conduit, and it is stamped on the tool.

These are the common published figures. Benders from different manufacturers differ by up to a quarter inch — which is a quarter inch of error on every stub you make, so read your own tool rather than this table.

Why offsets come out crooked

• The two bends are not in the same plane. The conduit must be rotated exactly 180° in the bender between them. Any error shows up as a dog-leg. Sighting down the pipe before the second bend catches it.
• Bending from the wrong side of the mark. This changes the offset depth without looking obviously wrong, so it is found at the box rather than at the bender.
• Over-bending and correcting. Pulling a bend back work-hardens the conduit and flattens the wall on the inside of the curve, which reduces the internal cross-section available for conductors.
• Shrink not added. The bends are right, the pipe is short.

How much bend a run is allowed

NEC 344.26 and its equivalents for other raceway types limit a run to 360 degrees total between pull points — four 90° bends, or any combination summing to the same. Note that offsets count: two 30° bends are 60° of the budget.

The limit is about pulling tension, not the conduit. Every bend multiplies the force needed rather than adding to it, so the fourth 90° costs far more than the first. Chapter 9 Table 2 also sets a minimum bend radius by conduit size, which is what stops a tight bend flattening the raceway.

Once the conduit is in, our conduit fill calculator checks the conductors fit it, and box fill handles the boxes at each end.

How this calculator is checked

Technical reviewer

Salamot Hok

Electrician · 10+ years of installation work in Bangladesh and the wider South Asian region

He reads the result the way an installer would: are the defaults values people actually meet, does the warning fire where you would stop and think, and is the answer something you could buy and fit? The code figures themselves come from the published standards cited below, not from him — that boundary is set out on his profile.

• The maths lives in a pure function with its own test suite, asserted against worked examples from published references and standards. A calculator does not ship until those tests pass.
• 2 sources cited by name and linked, so any figure on the page can be traced back to the document it came from.
• Last reviewed 17 August 2026. Review dates are advanced only when the page is actually re-read, never to look fresh.
• Unusable input returns no answer. Where the inputs do not describe a real design, the calculator says so and withholds the number rather than printing a plausible-looking wrong one.

The full process is written up in the methodology and editorial policy. Results are engineering guidance, not a code sign-off — see the disclaimer. If a result looks wrong, tell us; corrections are answered before anything else.