Conduit Fill Calculator FAQ

Yes, the conduit fill limits are based on NEC 2026 planning values for the selected conduit type and conductor count. However, local jurisdictions may still enforce an earlier edition — always confirm the adopted code year before relying on the results for permit or inspection purposes.

Yes, each row has its own size, source, and quantity settings. The calculator sums the actual cross-sectional area across all rows before applying the appropriate fill limit based on total conductor count. This enables mixed power and data cable runs in a single conduit.

Brand rows provide seed outside-diameter records for common Southwire building wire and Belden data cable products. These seed values are typical catalog dimensions and are useful for quick planning, but you should always verify against the exact manufacturer datasheet before ordering materials or committing to a design.

Yes, data mode includes Belden Cat5e, Cat6, Cat6A, and Cat7 seed rows and applies a 40% planning fill limit with a bend-radius reminder. Data cables have larger ODs than individual THHN conductors, so they consume fill quickly — a single Cat6 cable can use as much area as several power conductors.

NM-B (Romex) can run in conduit in certain situations, but NEC Article 334 restricts its use in wet locations and in raceways longer than necessary for physical protection. The calculator flags NM-B rows so you can verify the installation complies with local code and the specific conduit application.

The calculator supports EMT (Electrical Metallic Tubing), PVC Schedule 40/80, RMC (Rigid Metal Conduit), and ENT (Electrical Nonmetallic Tubing). Each type has different internal diameters for the same trade size, and the calculator uses the correct NEC table values for each material.

Yes, the calculator includes a chart view of fill percentages across conduit runs and an Excel export feature for printing job site documentation or submitting fill calculations with permit applications.