What is the maximum safe length for a 14-gauge extension cord carrying 10 amps?

50 feet is fine, but 100 feet is pushing it. At 10 amps on 14-gauge, you lose about 2% voltage per 50 feet — fine for lights and most tools. At 100 feet, a 4% drop can dim lights and annoy some motors. If you need 100+ feet, step up to 12-gauge.