Rigid (RMC), IMC and EMT conduit sizes to 4 in: outside diameter, wall and inside diameter by trade size, inches and mm — dimension sheet Source: Xem Studio, https://xemstudio.com/objects/rigid-imc-emt-conduit-sizes-to-4-in/ (sheet CC BY 4.0) Basis: Wheatland Tube (RMC OD and ID), BIA conduit catalog (walls, EMT 2-1/2 to 4), Allied Tube IMC cut sheet; numbers only, disagreements shown Catalog version: 2026-10-20 Sizes: see table below - Rigid metal conduit (RMC, also called GRC, galvanized rigid conduit): OD and ID by trade size from Wheatland Tube's submittal sheet (ANSI C80.1, UL 6; its OD tolerance is ±0.015 in for 1/2 to 1-1/2 in and ±1% for 2 in and up); walls from BIA's conduit page. BIA prints the rigid OD rounded to 0.1 in (0.8, 1.0, 1.3 ...) so its OD is not used; Wheatland's nominal ID agrees with BIA's wall on every row (OD − ID = 2 × wall to 0.0015 in). - IMC (intermediate metal conduit, ANSI C80.6): Allied Tube's cut sheet gives OD and wall; BIA's catalog page prints a thicker wall for every size (for 1/2 in: Allied 0.070 in, BIA 0.078 in; for 4 in: 0.140 and 0.150), so both are shown and the ID is computed from Allied's wall. Check the maker's sheet for the one you buy. BIA's rounded IMC OD is not used. - EMT sizes 1/2 to 2 in are on the emt-conduit page (OD 0.706 to 2.197 in); this page adds 2-1/2 to 4 in from BIA's conduit page (ANSI C80.3): the wall is printed there and the ID is computed. Only one source was read for them. BIA's EMT values for 1/2 to 2 in agree with the emt-conduit page. - Trade size (and the metric designator 16 to 155) identifies the size; per the Steel Tube Institute 'they are for identification purposes only and are not actual dimensions'. Knockout diameters for the same trade sizes are on the knockout page. - Left out: thread dimensions and lengths of rigid and IMC (the threads are NPT-style conduit threads with their own lengths), bend radii, coupling and fitting dimensions: the set-screw EMT connector and coupling sheets read (EMCO ERI, O-Z/Gedney) print drawing dimensions as A, B, C without saying which each is, so none is tabulated. No files: a conduit stick is a plain tube; the OD and wall are the numbers. type trade size (in) metric designator OD (in) OD (mm) wall (in) wall, second source (in) ID (in) rigid (RMC / GRC, ANSI C80.1) 1/2 16 0.840 21.34 0.104 - 0.632 (printed) rigid (RMC / GRC, ANSI C80.1) 3/4 21 1.050 26.67 0.107 - 0.836 (printed) rigid (RMC / GRC, ANSI C80.1) 1 27 1.315 33.40 0.126 - 1.063 (printed) rigid (RMC / GRC, ANSI C80.1) 1-1/4 35 1.660 42.16 0.133 - 1.394 (printed) rigid (RMC / GRC, ANSI C80.1) 1-1/2 41 1.900 48.26 0.138 - 1.624 (printed) rigid (RMC / GRC, ANSI C80.1) 2 53 2.375 60.33 0.146 - 2.083 (printed) rigid (RMC / GRC, ANSI C80.1) 2-1/2 63 2.875 73.03 0.193 - 2.489 (printed) rigid (RMC / GRC, ANSI C80.1) 3 78 3.500 88.90 0.205 - 3.090 (printed) rigid (RMC / GRC, ANSI C80.1) 3-1/2 91 4.000 101.60 0.215 - 3.570 (printed) rigid (RMC / GRC, ANSI C80.1) 4 103 4.500 114.30 0.225 - 4.050 (printed) rigid (RMC / GRC, ANSI C80.1) 5 129 5.563 141.30 0.245 - 5.073 (printed) rigid (RMC / GRC, ANSI C80.1) 6 155 6.625 168.28 0.266 - 6.093 (printed) IMC (ANSI C80.6) 1/2 16 0.815 20.70 0.070 (Allied) 0.078 (BIA) 0.675 (computed, Allied wall) IMC (ANSI C80.6) 3/4 21 1.029 26.13 0.075 (Allied) 0.083 (BIA) 0.879 (computed, Allied wall) IMC (ANSI C80.6) 1 27 1.290 32.76 0.085 (Allied) 0.093 (BIA) 1.120 (computed, Allied wall) IMC (ANSI C80.6) 1-1/4 35 1.638 41.60 0.085 (Allied) 0.095 (BIA) 1.468 (computed, Allied wall) IMC (ANSI C80.6) 1-1/2 41 1.883 47.82 0.090 (Allied) 0.100 (BIA) 1.703 (computed, Allied wall) IMC (ANSI C80.6) 2 53 2.360 59.94 0.095 (Allied) 0.105 (BIA) 2.170 (computed, Allied wall) IMC (ANSI C80.6) 2-1/2 63 2.857 72.56 0.140 (Allied) 0.150 (BIA) 2.577 (computed, Allied wall) IMC (ANSI C80.6) 3 78 3.476 88.29 0.140 (Allied) 0.150 (BIA) 3.196 (computed, Allied wall) IMC (ANSI C80.6) 3-1/2 91 3.971 100.86 0.140 (Allied) 0.150 (BIA) 3.691 (computed, Allied wall) IMC (ANSI C80.6) 4 103 4.466 113.43 0.140 (Allied) 0.150 (BIA) 4.186 (computed, Allied wall) EMT (ANSI C80.3), sizes above the emt-conduit page 2-1/2 63 2.875 73.00 0.072 (BIA) - 2.731 (computed) EMT (ANSI C80.3), sizes above the emt-conduit page 3 78 3.500 88.90 0.072 (BIA) - 3.356 (computed) EMT (ANSI C80.3), sizes above the emt-conduit page 3-1/2 91 4.000 101.60 0.083 (BIA) - 3.834 (computed) EMT (ANSI C80.3), sizes above the emt-conduit page 4 103 4.500 114.30 0.083 (BIA) - 4.334 (computed) Files elsewhere (not hosted by Xem Studio; license as stated by the publisher): - Wheatland Tube: Rigid Metal Conduit submittal sheet (Canada, English): nominal OD and ID by trade size 1/2 to 6, ANSI C80.1, UL 6 — web — Publisher's page; dimensions are facts — https://www.wheatland.com/wp-content/uploads/2022/05/Rigid-Metal-Conduit-Submittal-Sheet-–-Canada-English.pdf - BIA (biaonline.com): Conduit catalog page 7201: GRC (ANSI C80.1), IMC (ANSI C80.6) and EMT (ANSI C80.3) OD, wall by trade size (OD of GRC and IMC printed rounded to 0.1 in) — web — Publisher's page; dimensions are facts — https://www.biaonline.com/catalog/pdfs/72/7201.pdf - Allied Tube & Conduit (utilitypipesupply.com copy): IMC cut sheet: OD and wall by trade size 1/2 to 4 (ANSI C80.6, UL 1242) — web — Publisher's page; dimensions are facts — https://utilitypipesupply.com/cdn/shop/files/Allied_Tube_Conduit_IMC_Cut_Sheet.pdf - Steel Tube Institute: Steel conduit and EMT metric designators (trade sizes are for identification, not actual dimensions) — web — Publisher's page; dimensions are facts — https://steeltubeinstitute.org/faq/steel-conduit-emt-metric-designators/ No true-size file yet: the published figures do not fix the whole shape; a measured scan is planned. API: https://xemstudio.com/api/geometry?object=rigid-imc-emt-conduit-sizes-to-4-in