About & Methodology
How every wire size, ampacity and voltage-drop result on this site is calculated and verified against the 2023 National Electrical Code.
WireSizeCalculator.org is a free reference tool for sizing electrical conductors, breakers and voltage drop to the U.S. National Electrical Code. Every number it returns is computed directly from the published NEC tables below — not estimated, and not copied from other websites.
How we verify accuracy
- Every result is generated from the 2023 NEC tables listed below — the same tables a licensed electrician uses.
- Outputs are cross-checked against known reference values (e.g. 50A → 8 AWG copper, 100A → 3 AWG, 200A → 3/0) before publishing.
- We apply the rules that change the answer — the 240.4(D) small-conductor limits, 110.14(C) termination temperatures, the 125% continuous-load rule and voltage drop — rather than a single lookup.
- Content was last reviewed against the 2023 NEC in June 2026.
The NEC 2023 sources we use
| NEC reference | What it governs |
|---|---|
| Table 310.16 | Conductor ampacities (60 / 75 / 90°C, copper & aluminum) |
| 240.6(A) | Standard overcurrent device (breaker/fuse) sizes |
| 240.4(D) | Small-conductor overcurrent limits (14/12/10 AWG) |
| 110.14(C) | Termination temperature limits |
| 310.15(B)(1) | Ambient-temperature correction factors |
| 310.15(C)(1) | Conductor-bundling adjustment factors |
| 210.19 / 215.2 | Continuous-load 125% conductor sizing |
| Chapter 9, Table 8 | Conductor DC resistances (voltage drop) |
Safety disclaimer
This tool provides reference calculations only and is not a substitute for professional electrical engineering or design. Electrical work must comply with the edition of the NEC and any local amendments adopted in your jurisdiction, and with manufacturer instructions. Motors, HVAC and welders follow special rules (NEC 430/440/630). Always have installations designed and inspected by a licensed electrician. You assume all responsibility for use of this tool.