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Standard conduit trade sizes run 1/2, 3/4, 1, 1-1/4, 1-1/2, 2, 2-1/2, 3, 3-1/2, 4, 5, and 6 inches. The same trade sizes apply across EMT, PVC, RMC, and IMC, though the actual interior dimensions differ by raceway type.

No. Trade size is a nominal label, not a measurement. A 1/2-inch EMT has an interior diameter of about 0.622 inches, and PVC or RMC of the same trade size differ again. Always use the true interior diameter from NEC Chapter 9, Table 4 for fill calculations.

For typical 15 and 20 amp branch circuits with a few 14 or 12 AWG conductors, 1/2-inch conduit is the common residential size. Larger feeders, service runs, and multi-circuit home runs step up to 3/4-inch or 1-inch depending on conductor count.

Common standard boxes include the 4-inch square (often called a 1900 box) and 4-11/16-inch square, plus single- and multi-gang device boxes. Box fill is calculated by cubic-inch volume under NEC 314.16, which is a separate rule from conduit fill.

No. At the same trade size, EMT, PVC Schedule 40, PVC Schedule 80, RMC, and IMC each have different wall thicknesses and therefore different interior areas. That is why conduit fill depends on both trade size and raceway type.