Conduit Fill

Plan from visible inputs

Choose a conduit type, a nominal trade size from ½ inch to 4 inches, a stranded copper wire size from 14 AWG to 4/0, THHN or THWN-2 insulation, and a count from one to 40. The result shows fill percentage and an illustrative cross-section.

Wire and bore areas are calculated from published manufacturer dimensions. The general comparison changes with the conductor count: 53% for one, 31% for two, and 40% for three or more. These are planning comparisons, not a determination of code compliance.

Free checks and one-time options

The free tier provides one fill check per app session and three per day. Lifetime unlocks unlimited checks and reverse sizing. Reverse Size can also be purchased separately; it shows the next trade size and the smallest fitting size at or above your selection, while ordinary fill checks retain the free limits.

Know the scope

Only individual insulated stranded copper wires of one size are supported. Count every wire in the conduit, including neutral and grounding wires. Mixed wire sizes, bare grounds, and cable assemblies need a separate calculation.

The app does not evaluate ampacity, derating, pulling tension, jamming, bends, or special fill exceptions. Manufacturer tolerances and the locally adopted code matter. Consult a licensed electrician before work. Settings → Sources & assumptions provides the exact references, units, and limitations.

Purchases through Apple

Available options and current localized prices appear in the app before purchase. Apple processes payments. The optional add-ons are one-time purchases, with no recurring subscription.

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