Extension Cord Gauge Chart
An undersized extension cord is one of the most common and most dangerous mistakes in a home workshop: the cord heats up, the tool receives less voltage than it needs, and the motor draws more current to compensate, which damages the tool and risks a fire. This chart matches wire gauge to amperage and cord length so you can pick a cord that actually carries the load.
How AWG numbering works
American Wire Gauge runs backwards from intuition: a lower number means a thicker wire. 12 AWG is substantially thicker and carries far more current than 16 AWG. Common extension cord gauges are 16, 14, 12, and 10 AWG, in ascending order of capacity.
Cord labels usually show gauge and conductor count together, like '12/3', meaning 12 AWG wire with 3 conductors (hot, neutral, ground). Always use a 3-conductor grounded cord for power tools.
Gauge by amperage and length
Up to 7 amps: 16 AWG works to 25 feet, 14 AWG to 50 feet, 12 AWG to 100 feet. Suitable for lights, small hand tools, and chargers.
7 to 10 amps: 16 AWG to 25 feet, 14 AWG to 50 feet, 12 AWG to 100 feet. Covers most drills, sanders, and jigsaws.
10 to 12 amps: 14 AWG to 25 feet, 12 AWG to 50 feet, 10 AWG to 100 feet. Circular saws and routers sit here.
12 to 15 amps: 14 AWG to 25 feet, 12 AWG to 50 feet, 10 AWG to 100 feet minimum. Table saws, compressors, and large shop vacs.
The pattern is simple: every doubling of cord length needs roughly one step thicker wire to carry the same current safely.
Why length matters as much as amperage
Resistance increases with cord length, causing voltage drop: the tool at the far end receives less than the 120V it expects. A motor starved of voltage draws extra current to produce the same power, which generates heat in both the motor and the cord.
This is why a 100 foot 16 AWG cord that feels fine powering a work light becomes genuinely hazardous with a circular saw on the end. The tool may still run, which is exactly what makes the mistake easy to miss until the cord is hot to the touch.
Practical cord rules
Never daisy-chain extension cords: each connection adds resistance and the combined length almost always exceeds what the gauge supports. Use one correctly sized cord instead.
Unroll a cord completely before use. A coiled cord under load acts like an induction coil and traps heat, and cords have melted while still on the reel at loads they would carry fine when fully extended.
Check the cord's own amperage rating printed on the jacket, use outdoor-rated (W or SJTW) cords outdoors, and replace any cord with damaged insulation rather than taping it.