1. Calculate occupied area
We add each insulated conductor’s Chapter 9 Table 5 area multiplied by its quantity, including grounds. We compare that sum with the published allowable area for the conduit and conductor count in Table 4.
The verdict uses integer units of 0.0001 square inches, with the same-size Note 7 allowance where applicable. Rounding the displayed percentage never changes a verdict.
2. Find the limiting ampacity
For each circuit conductor group: 90°C base ampacity × conductor-count factor × ambient-temperature factor. Then take the smaller of that result and the selected termination-column ampacity. The lowest group result controls.
The entered load applies to every circuit group. For different-load circuits, the highest requirement gives a conservative screen. An individual-circuit analysis must still include every conductor in the shared raceway for fill and current-carrying count.
3. Compare all checked limits
PASS requires acceptable fill, adequate adjusted ampacity, and compliance with the ordinary small-conductor protection ceiling. A missing or unsupported input produces no verdict. Changing a setup removes the old verdict until you check again.
The continuous-load switch compares 125% of the entered load with the adjusted capacity and small-wire ceiling. This deliberately conservative screen can reject a setup that a complete NEC sizing analysis would accept. Mixed loads and 100%-rated assembly exceptions need separate analysis.
Supported inputs
EMT, PVC Schedule 40, RMC, and IMC, from ½ to 2 inches. Conventional noncompact, insulated THHN/THWN-2: copper #14–#2 AWG and aluminum #12–#2 AWG. Standard raceway runs longer than 24 inches; ambient temperatures from 26°C to 60°C.
Grounds entered here are insulated conductors. Bare grounds, cables, compact conductors, nipples, other insulation types, and sizes outside this catalog are not interchangeable with these inputs.
What this result does not establish
It does not check voltage drop, pulling tension, jam ratio, bend count, box fill, equipment-ground sizing, bonding, raceway suitability, parallel conductors, motor/HVAC exceptions, rooftop adders, or final breaker selection. It cannot decide which neutrals qualify for exclusion.
An acceptable electrical fill percentage does not guarantee an easy physical pull. Verify the actual installation, equipment listings, adopted code, and local inspector’s requirements before work.
Sources and review status
This is an implementation preview, not an independently certified calculation service. Table samples have been cross-checked against published manufacturer material and accessible code reproductions; several reproductions are from earlier editions. Automated tests verify the implemented behavior but do not replace electrical review.
Before public release, a qualified electrical reviewer must check every supported table cell and rule against the licensed NEC 2023 edition. Review status: pending. Last implementation audit: September 26, 2026.