How many amps can I run on a 14 gauge wire?

Fourteen gauge copper runs 15 amps on a breaker, full stop for ordinary branch circuits. NEC 240.4(D) pins it there even though the raw table ampacity reads 20 at 75C.

That margin is deliberate; homes bundle cable through insulation and load circuits unpredictably, and the small-conductor rule absorbs all of it.

So 14 gauge on a 20 amp breaker is a violation and a fire pattern, not a gray area. The one legitimate exception family is motor and HVAC circuits, where the equipment's overload device protects the wire and the breaker only handles faults.

Fifteen amps at 120 volts is 1,800 watts; a space heater plus almost anything else exceeds it. That is why kitchens get 12 gauge.

The 14 gauge amperage calculator lays out the limit and the exceptions with citations.