50 feet is the safe limit for a standard extension cord on a 15-amp circuit.

It depends on the wire gauge, but for a typical 14-gauge cord, keep it under 50 feet if you’re pulling the full 15 amps. Go longer and voltage drop will kill performance.

Voltage drop is the issue. More than 3% drop (about 3.6 volts) and motors run hotter, lights dim, and tools lose power. A 14-gauge cord at 50 feet stays under that threshold at 15 amps. At 100 feet you’re looking at a 7% drop—bad news.

If you genuinely need 100 feet, step up to a 12-gauge cord. That’ll handle the length at full load. But don’t cheat with a thinner cord; it’s a fire hazard.

Your tools and your panel will thank you for not pushing it.