Estimates only. These results may be wrong for your specific installation, and they are not engineering or code-compliance advice. Check every result against the code that applies to you and with your local inspector (AHJ) before you install anything. Terms of Service
Look up one answer at a time: wire size for a load, the current a wire carries, ground wire size, control wire, or temperature correction. Values come from common industry conductor tables for insulated copper and aluminum wire.
Your wire
How the conductor reference works
One question at a time: what wire size for this load, what current does this wire carry, what ground wire for this breaker, what control wire, or how much does ambient temperature change the answer. Values come from common industry conductor tables for insulated copper and aluminum wire.
Steps
- Choose a tab: Wire for a load, Current a wire carries, Ground wire, Control wire or Temperature correction.
- Enter the load or choose a wire size, then pick copper or aluminum, inside a panel or field wiring, and the insulation temperature rating.
- Read the answer and the note under it, which says when other rules such as derating apply.
- For derating, voltage drop and the breaker, use the Wire and breaker sizing calculator.
Example
More than three current-carrying conductors in one raceway call for the current to be reduced: by 80% for 4–6 conductors, 70% for 7–24, 60% for 25–42 and 50% for 43 or more, as the reference page notes.
Questions
- Is this a copy of the code tables?
- It is a convenience reference built from commonly used conductor tables. It is not the code. Use your own copy of the adopted code for anything that matters.
- Why separate inside-panel and field wiring?
- Panel wiring is commonly sized from a different table than field conductors. The tool follows that split so you can see both.
- Does it cover temperature correction?
- Yes. Enter the ambient temperature and the insulation rating and it shows the correction factor.
The code references on this page are pointers, not a substitute for the code. NEC® and National Electrical Code® are registered trademarks of the National Fire Protection Association (NFPA). WireAndWidgets is not affiliated with or endorsed by NFPA. Rules differ by edition and by local amendment, so check the code your inspector (AHJ) enforces before you build or install anything.