What this table represents
The ampacity values are base current-carrying capacities for copper conductors, PVC insulation, single circuit, at 30°C ambient — a common reference condition used as a baseline before real-world derating is applied.
Why this isn't a final answer
Actual safe ampacity depends on several factors this reference table doesn't capture: installation method (conduit, free air, buried, bundled), ambient temperature away from 30°C, grouping with other loaded circuits, and insulation type. Full derating tables are published in governing standards — IEC 60364-5-52 internationally, or NEC 310.16 in the US — and should be the final reference for any real installation.
Frequently asked questions
Is this table safe to use for a final electrical design?
No — treat it strictly as a starting point. Undersizing a cable is a fire risk. Always apply your governing code's full derating tables and, for anything beyond a simple reference check, have a qualified electrician verify the final cable size.
Why would my cable need to be bigger than this table suggests?
Common reasons: higher ambient temperature than 30°C, the cable is bundled or grouped with others (which raises heat build-up), it's buried or run in confined conduit rather than free air, or the run is long enough that voltage drop — not ampacity — becomes the limiting factor.
What's the difference between this and the Voltage Drop calculator?
This table checks whether a cable can safely carry the current without overheating (ampacity). The Voltage Drop calculator checks whether the cable stays within an acceptable voltage loss over its run length — a cable can pass one check and fail the other, especially on long runs.