Ambient Temperature Correction Factors
Correction-factor bands for common field temperatures, with a calculator handoff for exact sizing.
- Source
- ambient temperature correction factor table
- Edition
- 2023
- Updated
- 2026-07-27
- Scope
- United States
Lookup Table
How does ambient temperature change allowable ampacity?
| Ambient | 60 C column | 75 C column | 90 C column |
|---|---|---|---|
| 86 F / 30 C | 1.00 | 1.00 | 1.00 |
| 104 F / 40 C | 0.82 | 0.88 | 0.91 |
| 122 F / 50 C | 0.58 | 0.75 | 0.82 |
| 140 F / 60 C | - | 0.58 | 0.71 |
Calculated against the NEC 2023 edition using 310.15(B)(1). Confirm the edition adopted by your AHJ, which may differ and may carry local amendments.
Not covered by this tool
- Local amendments and equipment markings can be stricter than this reference view.
- Marginal values should be checked directly against the adopted edition.
- This page is a routing aid and does not replace the owning calculator for project-specific inputs.
Data last verified