Find the amps on the nameplate of the tool or appliance, then read the gauge for your cord’s length from a maker’s chart. The charts don’t agree, so use the heaviest gauge any of them asks for, which is the lowest number.
The amps or watts are on the tool’s or appliance’s nameplate, the label with its ratings. For several things on one cord, type a sum, such as 8 + 4.5.
What gauge?
12 gauge
For 13 A over 50 ft, the heaviest gauge any of these makers’ charts asks for. A lower number is a heavier cord.
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DeWalt’s and Milwaukee’s tables give no cord at all for some loads and lengths, such as 13 amps over 100 feet.
Amps, watts and length
If the nameplate gives only watts, divide them by 120, the voltage DeWalt’s table is written for. A 1,500 watt load works out to 12.5 amps.
DeWalt’s and Milwaukee’s tables go by the length of the cord, and Carol’s chart by the farthest the tool or appliance will be from the outlet. When your length falls between two columns, read the longer one.
Extension cord gauge chart
Extension cord gauge
| Nameplate amps | 25 ft | 50 ft | 100 ft | 150 ft |
|---|---|---|---|---|
| Up to 6 A | 18 | 16 | 16 | 14 |
| Over 6 to 10 A | 18 | 16 | 14 | 12 |
| Over 10 to 12 A | 16 | 16 | 14 | 12 |
| Over 12 to 16 A | 14 | 12 | Not recommended | Not recommended |
Gauge (AWG) by the total length of the cord, from the manual for DeWalt’s DWS713 miter saw. If in doubt, use the next heavier gauge.
| Distance from the outlet | Up to 10 A | Up to 15 A |
|---|---|---|
| 0–25 ft | 16 | 14 |
| 25–50 ft | 16 | 14 |
| 50–75 ft | 16 | 12 |
| 75–100 ft | 16 | 12 |
Gauge (AWG), from Carol’s cord and cordset catalog.
| Southwire cord | 25 ft | 50 ft | 100 ft |
|---|---|---|---|
| 16 gauge | 13 A | 13 A | 10 A |
| 14 gauge | 15 A | 15 A | 13 A |
| 12 gauge | 15 A | 15 A | 15 A |
| 10 gauge | 20 A | 20 A | 20 A |
Pick the lightest Southwire cord rated for at least your load at your length.
| Nameplate amps | 25 ft | 50 ft | 75 ft | 100 ft | 150 ft |
|---|---|---|---|---|---|
| 0–2 A | 18 | 18 | 18 | 18 | 16 |
| 2.1–3.4 A | 18 | 18 | 18 | 16 | 14 |
| 3.5–5 A | 18 | 18 | 16 | 14 | 12 |
| 5.1–7 A | 18 | 16 | 14 | 12 | 12 |
| 7.1–12 A | 16 | 14 | 12 | 10 | None |
| 12.1–16 A | 14 | 12 | 10 | None | None |
| 16.1–20 A | 12 | 10 | None | None | None |
Gauge (AWG) by the length of the cord, from the manual for Milwaukee’s 5268-21 rotary hammer, based on limiting the voltage drop to five volts at one and a half times the rated amps. None: the table gives no gauge at that length.
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Why the gauge matters
Gauge is the size of the wire inside the cord. The lower the gauge, the more current the wire can carry, and the farther it can run from the outlet.
An undersized cord causes a drop in voltage, which means lost power and overheating. A light cord on a high-power tool, such as a saw, could damage the tool.
What’s printed on the cord
The wire size is printed on the cord’s surface, and the cord’s rating is on its tag or its packaging. Extension cords should be at least 16 AWG, unless they’re 18 AWG with fuse protection.
Extension cords are for temporary use. If any part of a cord is hot while in use, it may be overloaded. Unplug it. Check its rating against what’s plugged into it.