Wire Gauge to Breaker Size
Typical breaker sizes for copper conductors on a standard residential branch circuit — and the conditions that change them.
| Copper conductor | Typical breaker |
|---|---|
| 14 AWG | 15A |
| 12 AWG | 20A |
| 10 AWG | 30A |
| 8 AWG | 40A |
Read this before using any figure above. These are general-purpose values for 60°C-rated copper NM cable on a standard residential branch circuit. Actual ampacity changes with insulation rating, ambient temperature, and how many conductors are bundled together — in ways a fixed table cannot capture. They are a reference, not a substitute for the National Electrical Code as adopted and amended by your local authority having jurisdiction. Verify against local code before you wire anything.
Why this table is short
Four rows, not forty. These are the gauges that carry ordinary residential branch circuits, and they are the ones Varra will override its own answer with. Aluminium conductors, higher temperature ratings, derated bundles, and service-entrance sizing are all real and all absent, because publishing a number we have not verified would be worse than publishing nothing. The list grows as values are checked, not as pages are needed.
How Varra uses it
This is not a copy of what the engine knows — it is the same table, read straight out of the source. When a question turns on a specific gauge, Varra puts that gauge in its answer's label, and a matching row here replaces whatever the model stated from memory. Where the table has no row, Varra answers on its own and says so. That is the whole design: a model that defers on the numbers where being wrong costs something. It is the narrow, live edge of Varra Assurance — the layer that checks work before anyone acts on it.
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