Conduit Support Spacing Calculator
Look up the maximum National Electrical Code (NEC) support spacing for PVC, RMC, EMT, FMC, and LFMC by trade size, and the distance within which each run must be secured to a box. Enter a straight-run length to get the number of support points the run needs.
How to use this calculator
- Pick the conduit or tubing type: PVC, RMC, EMT, FMC, or LFMC.
- Pick the trade size. For rigid PVC and RMC the spacing steps up with size; for EMT, FMC, and LFMC the spacing is the same at every size.
- Optionally enter the straight-run length in feet to get the number of support points, counting a fastener at each end.
- Read the maximum spacing between supports and the distance within which the run must be secured to each box or termination.
NEC reference
This calculator follows the National Electrical Code (NEC) 2020 support and securing rules for each raceway type: rigid PVC conduit uses Table 352.30(B) and Section 352.30(A); rigid metal conduit (RMC) uses Table 344.30(B)(2) and Section 344.30(A); electrical metallic tubing (EMT) uses Section 358.30(A); flexible metal conduit (FMC) uses Section 348.30(A); and liquidtight flexible metal conduit (LFMC) uses Section 350.30(A). These spacings are unchanged in the 2017, 2020, and 2023 editions.
Results are for reference only. Verify against the applicable adopted edition of the NEC and consult a licensed electrician for code compliance.
How conduit support spacing works
Every raceway article in the NEC carries a support (securing) rule with two parts: a maximum distance between fasteners along the run, and a maximum distance from each box or termination within which the run must be secured. The spacing between fasteners is a fixed number for the flexible and thin-wall methods, and a value that increases with trade size for the rigid conduits, because a larger, stiffer conduit sags less between supports. The tool reads these maxima straight from the tables; you can always support a run more closely than the code minimum.
PVC support spacing (Table 352.30(B))
| Trade size (in.) | Max spacing between supports |
|---|---|
| 1/2 - 1 | 3 ft (900 mm) |
| 1-1/4 - 2 | 5 ft (1.5 m) |
| 2-1/2 - 3 | 6 ft (1.8 m) |
| 3-1/2 - 5 | 7 ft (2.1 m) |
| 6 | 8 ft (2.5 m) |
Section 352.30(A) also requires securing within 3 ft (900 mm) of each box, cabinet, or fitting.
RMC support spacing (Table 344.30(B)(2))
| Trade size (in.) | Max distance between supports |
|---|---|
| 1/2 - 3/4 | 10 ft (3.0 m) |
| 1 | 12 ft (3.7 m) |
| 1-1/4 - 1-1/2 | 14 ft (4.3 m) |
| 2 - 2-1/2 | 16 ft (4.9 m) |
| 3 and larger | 20 ft (6.0 m) |
Section 344.30(A) requires securing within 3 ft (900 mm) of each box or termination. Intermediate metal conduit (IMC) uses the same spacings under 342.30(B)(2).
EMT, FMC, and LFMC (fixed spacing)
| Type | Max spacing | Box-securing distance |
|---|---|---|
| EMT (358.30(A)) | 10 ft (3.0 m) | 3 ft (900 mm) |
| FMC (348.30(A)) | 4.5 ft (1.4 m) | 12 in. (300 mm) |
| LFMC (350.30(A)) | 4.5 ft (1.4 m) | 12 in. (300 mm) |
These spacings are the same for every trade size. FMC and LFMC are secured within 12 in. of a box, closer than the 3 ft allowed for the rigid methods and EMT.
Worked example: 45 ft of 3/4 in. EMT
- EMT under 358.30(A) is fastened at least every 10 ft, at any trade size.
- Number of gaps for a 45 ft run: 45 divided by 10 rounds up to 5 gaps.
- Support points, with a fastener at each end: 5 + 1 = 6.
- Each end fastener also satisfies the requirement to secure the run within 3 ft of the box it terminates in.
The support-point count is a planning estimate for a straight run fastened at both ends; it is not itself an NEC value, and closer support is always allowed.
Exceptions that allow longer unsupported lengths
The tool returns the base support rule. The NEC also allows longer unsupported lengths in specific cases: FMC and LFMC may be unsupported up to 900 mm (3 ft) at terminals where flexibility is needed, and up to 1.8 m (6 ft) for a luminaire whip tap; EMT may be fastened within 5 ft of a box where structural members do not readily permit fastening within 3 ft; and conduit run horizontally through holes in framing members is considered supported. Vertical risers and other wiring methods (NM, AC, MC cable, ENT, LFNC) have their own securing rules that are out of scope here.
Frequently asked questions
How far apart do conduit supports have to be?
It depends on the type and, for rigid conduit, the trade size. EMT is every 10 ft; PVC runs 3 to 8 ft; RMC runs 10 to 20 ft; FMC and LFMC are every 4.5 ft. Each run is also secured within 3 ft of a box (12 in. for FMC and LFMC).
Is the spacing a minimum or a maximum?
It is a maximum distance between supports. You can always fasten a run more closely; you cannot exceed the tabulated spacing.
Does IMC use the same spacing as RMC?
Yes. Intermediate metal conduit is supported per 342.30(B)(2), which lists the same distances as RMC Table 344.30(B)(2). Select RMC for an IMC run.
Why does PVC need closer support than metal conduit?
Rigid PVC is less stiff than steel conduit and sags more between supports, especially as it warms, so its support spacing is much shorter, 3 to 8 ft versus 10 to 20 ft for RMC of the same trade size.
Related calculators
- PVC Conduit Expansion Calculator: thermal length change of a PVC run and the 1/4 in expansion-fitting threshold.
- Conduit Fill Calculator: mixed conductors in EMT, RMC, IMC, or PVC against the Table 1 limits.
- Conduit Size Calculator: minimum trade size for a conductor bundle across all raceway types.
- Pull Box Size Calculator: minimum pull and junction box dimensions per NEC 314.28(A).
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