Who and why
Wire Ampacity Chart is an independent technical reference built to make the allowable ampacity values from NEC Table 310.16 fast, accessible, and intuitive to navigate. It is an independent publication and is neither produced by nor affiliated with the National Fire Protection Association (NFPA).
In practical electrical work, allowable copper and aluminum ampacities, small-conductor overcurrent protection limits under NEC 240.4(D), ambient temperature correction factors, and conductor bundling adjustments are scattered across separate tables and sections of the codebook. This tool consolidates these essential lookup tables and rules into a single, cohesive interface.
Sources
- NFPA 70, National Electrical Code (NEC), 2023 edition, Table 310.16: Allowable Ampacities of Insulated Conductors with not more than three current-carrying conductors in a raceway, cable, or direct burial, at 30°C (86°F) ambient.
- NEC Table 310.15(B)(1): Ambient temperature correction factors based on 30°C (86°F).
- NEC Table 310.15(C)(1): Conductor adjustment factors for more than three current-carrying conductors.
- NEC 240.4(D): Small-conductor rules for overcurrent protective devices.
- NEC 110.14(C): Conductor termination and equipment temperature rating requirements.
State and local jurisdictions may adopt different editions of the NEC or enforce local amendments. The link to NFPA directs to the standard developer's official site and does not constitute a licensed copy of the code.
Method
Every allowable ampacity value presented on this site is transcribed directly from the published NEC 2023 Table 310.16. Cell combinations not defined in the source standard remain blank. The Max column strictly displays the statutory small-conductor thresholds defined in NEC 240.4(D). For larger sizes not listed in 240.4(D), an em dash is displayed referencing NEC 240.4 for general overcurrent protection standards.
The downloadable PNG reference sheets and printable PDF are generated programmatically from the same underlying dataset to ensure complete consistency between web views and offline documentation. Automated unit tests verify key published figures, such as 14 AWG copper at 15 A, 20 A, and 25 A, as well as 4/0 copper at 195 A, 230 A, and 260 A.
Disclaimer
This website is provided solely as an informational reference. It does not replace the official National Electrical Code or published standards, nor does it provide licensed engineering, architectural, or legal advice. Always adhere to the electrical codes and ordinances adopted by your local authority having jurisdiction (AHJ). A licensed electrical professional should always calculate and verify temperature corrections, conductor bundling adjustments, termination temperature compatibility, and overcurrent protection sizing for any real-world electrical installation.