How it works
Distance between bends = rise × (1 / sin θ). Shrink = rise × shrink-constant(θ). Multiplier(30°) = 2, (45°) ≈ 1.41, (60°) ≈ 1.15.
The offset multiplier is just 1 / sin θ — that is the whole "magic number" chart: at 30° the conduit travels twice the rise between the two bends (multiplier 2.0), at 45° it is about 1.41, at 60° about 1.15. The smaller the angle, the longer the travel but the gentler the bend. Shrink happens because the conduit follows a longer diagonal path between the bends than the straight horizontal distance it covers, so the far end pulls back toward the bender — geometrically shrink = rise × (1 − cos θ) / sin θ, which the field charts round to 1/4 in per inch of rise at 30°, 3/16 at 22.5° and 3/8 at 45°. Forget to subtract the shrink and the conduit lands short of the next box. The minimum bend radius comes from NEC Chapter 9, Table 2 by conduit type and trade size — it is a property of the conduit and is met by using a code-rated bender shoe, so the calculator shows it as a reference figure rather than deriving a violation from your rise. For long pulls also size for voltage drop on the circuit, since an upsized conductor changes everything downstream.
Code references
- Radius of conduit and tubing bends NEC 2023, Chapter 9, Table 2 — centerline bend radii by trade size
- EMT minimum bending radius NEC 2023, 358.24
- IMC minimum bending radius NEC 2023, 342.24
- RMC minimum bending radius NEC 2023, 344.24
- Maximum 360° of bends between pull points NEC 2023, 300.24 (general) — EMT 358.26, IMC 342.26(B), RMC 344.26(B)
FAQ
What is shrink and why does it matter?
When you put an offset in a conduit, the pipe follows a longer diagonal path between the two bends than the straight horizontal distance it actually advances. That difference pulls the far end of the conduit back toward you — the "shrink." A 30° offset shrinks about 1/4 inch for every inch of rise, so a 4 in offset shrinks roughly 1 inch. If you measure to the box and cut without adding the shrink back, the conduit lands short. Always subtract the shrink from your measured run before cutting, or add it to the mark on the open end.
How many bends are allowed in one conduit run by the NEC?
No more than 360° total between pull points — that is four 90° bends, or any combination that sums to 360°. This is in NEC 300.24 as a general rule in the 2023/2026 cycle, and in the per-method sections: 358.26 for EMT, 342.26(B) for IMC and 344.26(B) for RMC. Past 360° the pulling tension climbs sharply and you risk damaging conductor insulation, so the fix is to add a pull box or conduit body to reset the count. This tool tracks the running total and warns you as you approach the limit.
What is the offset multiplier and where does it come from?
The multiplier is the number you multiply the rise by to get the distance between your two bend marks, and it is simply 1 / sin θ. At 30° that is 1 / 0.5 = 2.0, at 45° it is about 1.41, at 60° about 1.15. It is not a memorized magic number — it falls straight out of the right triangle formed by the rise (opposite side) and the conduit travel (hypotenuse).
How do I mark a 3-point saddle over a pipe?
Mark the center of the obstacle on the conduit — that is where the center bend goes, usually 45°. Then measure the side distance (rise × the multiplier for the side angle, usually 22.5°) on each side of the center mark for the two outer bends. The center bend goes up and over; the two outer bends bring the conduit back down to the original plane. If the obstacle is not centered on the stick, measure the center mark from a fixed reference rather than from the middle of the pipe.
How do I verify my bend angle in the field?
Use a magnetic digital angle finder stuck to the conduit, or a phone level app laid along the pipe after the bend. Bend slightly past your target to allow for spring-back (the conduit relaxes a degree or two after you release pressure), then check and nudge. Steel EMT springs back less than IMC or RMC.
Does the calculator handle different benders?
For 90° stubs, yes — enter your bender take-up (the deduct stamped on the hook). Greenlee benders are roughly 5 in for 1/2", 6 in for 3/4" and 8 in for 1" EMT; Klein and Ideal differ by up to 1/4 in. The mark for the stub is the desired stub height minus the take-up. For the most accurate number, do one test bend and measure the actual take-up of your specific bender.
This calculator is provided for estimation purposes. Bend dimensions vary with conductor, bender shoe and spring-back; always verify marks with a test bend and confirm radius and 360° limits against the current NEC edition and local amendments with a licensed electrician before bending.