EMT vs rigid conduit
By Andrew ·
Quick answer
EMT is thin-wall tubing joined with set-screw or compression fittings; rigid (RMC) is heavy-wall pipe that is cut and threaded, and IMC sits between them. At the same trade size rigid is fatter, 0.840" against 0.706" outside for 1/2", so it bends in a bigger groove with a bigger deduct, takes more force and springs back more.
EMT and rigid by trade size
| Trade size | EMT outside diameter | Rigid outside diameter | EMT deduct | Rigid deduct |
|---|---|---|---|---|
| 1/2" | 0.706" | 0.840" | 5" | 6" |
| 3/4" | 0.922" | 1.050" | 6" | 8" |
| 1" | 1.163" | 1.315" | 8" | 11" |
| 1-1/4" | 1.510" | 1.660" | 11" | — |
| 1-1/2" | 1.740" | 1.900" | — | — |
| 2" | 2.197" | 2.375" | — | — |
Three kinds of steel conduit
| EMT | IMC | Rigid (RMC) | |
|---|---|---|---|
| NEC article | 358 | 342 | 344 |
| Wall | Thin, not threaded | Between EMT and rigid, threaded | Heavy, threaded |
| Outside diameter, 1/2" | 0.706" | 0.815" | 0.840" |
| Outside diameter, 1" | 1.163" | 1.290" | 1.315" |
| Joined with | Set-screw or compression couplings and connectors | Threaded couplings and fittings | Threaded couplings and fittings |
| To carry and bend | Lightest | Lighter than rigid | Heaviest |
EMT isn’t threaded; its wall is too thin. That drives most of the difference on the job. EMT is cut, reamed and pushed into a fitting. Rigid and IMC are cut, reamed and threaded, so the cut length has to be right before the threader comes out, and every piece is heavier to carry, hang and bend.
Where each is used
- EMT is the everyday raceway for exposed and concealed runs in commercial buildings: light, quick to bend and quick to join.
- Rigid goes where the conduit needs the most protection from physical damage, and is common for service masts, outdoor runs and many hazardous (classified) locations.
- IMC is generally allowed in the same places as rigid, with a thinner wall that is lighter to carry and bend.
The rules are in NEC Articles 358 (EMT), 342 (IMC) and 344 (RMC), and your local code and inspector decide what a given job allows. All three use the same minimum bending radius, from Chapter 9, Table 2, and all three limit the bends between pull points to 360° in total.
How bending differs
- A bigger groove. On a hand bender, rigid rides in the head one EMT size up. On the Greenlee iron bender, 1/2" rigid bends in the 3/4" EMT head and deducts 6", where 1/2" EMT deducts 5".
- A bigger radius. The bigger head brings a bigger radius, 5 1/8" against 4 3/16" at 1/2", so rigid marks differ more from a sharp-corner chart.
- More force. Hand benders take rigid only to 1". Above that you need a mechanical, electric or hydraulic bender.
- More springback. The heavy wall springs back more than EMT, so bend slightly past the angle and check with a level.
- Separate shoes on power benders. Electric and mechanical benders have their own rigid and EMT shoes or grooves, and many bend IMC in the rigid shoe.
- Stub length
- 12"
- 1/2" EMT
- Mark at 7", a 5" deduct
- 1/2" rigid
- Mark at 6", a 6" deduct
IMC is a little slimmer than rigid, 1.290" against 1.315" outside at 1", and many benders bend it in the rigid shoe with the rigid deduct. A few list their own IMC numbers: the Greenlee 555’s multi-shoe group deducts 13 3/4" for 1-1/2" IMC and 14 1/4" for rigid. Pick the type you are actually bending.
Bending either in BendMate
BendMate has EMT, rigid and IMC shoes for every bender that takes them, each with its own outside diameter, radius and deduct, and every mark is worked out from the shoe you pick. With a hand bender, offsets, 3- and 4-point saddles, 90s and kicks are free with no signup. Rigid above 1" calls for a mechanical, electric or hydraulic bender, which are part of Pro, $5.99 once.
Get the marks for your bender
BendMate works this out from your bender’s radius and deduct, flags a bend that won’t work, and shows you every mark.
Free for offsets, saddles, 90s and kicks with a hand bender. No signup.
Common questions
What is the difference between EMT and rigid conduit?
EMT is thin-wall tubing joined with set-screw or compression fittings. Rigid is heavy-wall pipe joined by threads, heavier and stronger, and slightly larger outside at the same trade size.
Is IMC the same as rigid?
No. IMC is threaded like rigid, but its wall is thinner, so it is lighter and slightly smaller outside. Many benders bend it in the rigid shoe, but check your bender’s chart for IMC.
Can you bend rigid with an EMT bender?
Only in the head marked for it. Rigid rides one head up on a hand bender, so a 3/4" EMT head bends 1/2" rigid, with that head’s 6" deduct.
Is the take-up the same for EMT and rigid?
Not at the same trade size. On a Greenlee iron hand bender, 1/2" EMT deducts 5" and 1/2" rigid deducts 6", because rigid bends in the bigger head.
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