Conductor Adjustment Factors
NEC 2020 — Table 310.15(C)(1)
| Number of conductors | Percent of adjusted ampacity |
|---|---|
| 4–6 | 80% |
| 7–9 | 70% |
| 10–20 | 50% |
| 21–30 | 45% |
| 31–40 | 40% |
| 41 and above | 35% |
For one to three current-carrying conductors, no adjustment factor is applied. Count conductors as required by the applicable code rules.
Source: NEC 2020 Table 310.15(C)(1). Verify requirements against the locally adopted code and applicable amendments.