What gauge extension cord should I use for a leaf blower at 100 feet?

Use a 12-gauge extension cord for a leaf blower at 100 feet. A thinner 14-gauge cord drops 5-6 volts, cutting air velocity by 10-20% and making the motor run hotter, while a 12-gauge cord drops only about 3 volts. If you already have a 14-gauge 100-footer, use it for lights or a hedge trimmer instead.