What size extension cord can I use on my generator?

120 Volt Receptacles WATTS 25 FEET 50 FEET 100 FEET 2500-3750 16 gauge 14 gauge 12 gauge 4000-6500 14 gauge 12 gauge 10 gauge 7000-10000 12 gauge 10 gauge 8 gauge 240 Volt Receptacles WATTS 25 FEET 50 FEET 100 FEET 2500-3750 14 gauge 12 gauge 10 gauge 4000-6500 12 gauge 10 gauge 8 gauge 7000-10000 10 gauge 8 gauge 6 gauge