Frequently Asked Questions

No. The calculator library is available without registration. Favorites and recent calculation history are designed to stay in your browser on the device you use.

Yes. Public pages and calculator screens are built for both desktop and mobile review, including quick checks away from the office.

Confirm the system type, voltage basis, conductor material, termination temperature basis, and distance or load units before using any result for planning or comparison.

Yes. Share the calculator page URL so the same workflow opens directly. If you are reporting an issue, include that page URL and the exact inputs you used.

The site is written for the U.S. market. Many pages reference NEC rules or common U.S. electrical practice, while some screens are engineering reference tools rather than direct code-compliance engines.

No. Use the calculators for screening, comparison, and preliminary planning. Final design decisions, field conditions, local amendments, and inspection requirements still need review by the responsible designer, AHJ, or licensed professional.

THHN or THWN-2 insulation may be rated 90C, but many terminals are limited to 75C. Under NEC 110.14(C), the final ampacity used at the termination cannot exceed the lowest temperature rating in the connection path. That is why many conductor-sizing screens use 90C for adjustment steps and then cap the final answer at the applicable 75C termination limit.

For a continuous load, the overcurrent device usually has to be sized for 125% of that load. In everyday planning language, that means a standard circuit is typically not intended to carry more than 80% of its rating continuously for three hours or more.

Yes. Local jurisdictions, utility rules, project specifications, and equipment listings can change the final requirement even when a calculator reflects a common NEC starting point.

Favorites and recent history are intended to stay in local browser storage. If you contact support, only the details you send directly in that message are available to the team.

Send the page URL, the input values, the result you saw, and why it looked wrong or incomplete. A screenshot helps when the issue is visual or device-specific.

Yes. Use the contact page and describe the workflow or question you want covered so it can be reviewed against the current U.S.-market library.

Report the mismatch with the exact page URL and the section or result that looks inconsistent. That makes it easier to review the page text and calculator result together.