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CordGauge Guide

Independent AWG directory

Pick an extension cord by amps, then length, then AWG

CordGauge Guide is a comparison hub for shop and DIY tools. Jacket color and “heavy duty” on the hang tag do not tell you whether a 15 A circular saw will sag at 100 feet. Nameplate amps and run length do.

How to pick a cord

  1. Step 1

    Read the tool amps

    Use the nameplate, not the marketing box. A circular saw that says 15 A is a 15 A load even if the cut “feels light.”

  2. Step 2

    Measure the run

    Length is outlet to tool, including any extra coil you leave on the ground. Two 50-foot cords in series are a 100-foot problem plus an extra connection.

  3. Step 3

    Pick AWG for drop, then check the mark

    Thicker copper (smaller AWG number) drops less voltage. Then confirm the cord and plug are listed for at least the tool’s amps. A 12 AWG cord with a 15 A plug is still a 15 A cord.

Gauge calculator

Planning estimate for a 120 V copper cord. The marked ampacity on the cord still wins if it is lower. This does not size a new circuit.

Shop pick: 12 AWG

12 AWG drop at 15 A · 50 ft: 2.9 V (2.4%)

14 AWG
4.6 V (3.8%)
12 AWG
2.9 V (2.4%)
10 AWG
1.8 V (1.5%)

  • Southwire 12/3 SJTW 50 ft outdoor

    12 AWG · 50 ft · SJTW outdoor, lighted end, marked 15 A

    View on Amazon

  • Southwire 12/3 SJTW 100 ft outdoor

    12 AWG · 100 ft · SJTW outdoor, lighted end, marked 15 A

    View on Amazon

15 A shop loads, at a glance

Full gauge × amps × length chart

Copper planning drop at 120 V (NEC Ch. 9 Table 8 resistances). Aim near 3% for motor tools. The marked ampacity on the cord still wins if it is lower.

RunShop pick14 AWG drop12 AWG drop10 AWG drop
25 ft · 15 A12 AWG2.3 V (1.9%)1.4 V (1.2%)0.9 V (0.8%)
50 ft · 15 A12 AWG4.6 V (3.8%)2.9 V (2.4%)1.8 V (1.5%)
100 ft · 15 A10 AWG9.2 V (7.7%)5.8 V (4.8%)3.6 V (3.0%)

50 ft 12 AWG SJTW is the usual shop buy for the 50-foot row. At 100 feet the chart pick is 10 AWG.

Shop outdoor cords

Named SJTW cords checked against the Amazon listing for gauge, length, and a live buy box. Links go to Amazon (Associates tag laqaer-20). We may earn a commission. No scores and no prices.

  • Southwire 12/3 SJTW 50 ft outdoor

    12 AWG · 50 ft · SJTW outdoor, lighted end, marked 15 A

    View on Amazon

  • Southwire 12/3 SJTW 100 ft outdoor

    12 AWG · 100 ft · SJTW outdoor, lighted end, marked 15 A

    This is a 12 AWG cord. At 100 ft and 15 A the copper estimate is about 5.8 V (4.8%). The chart pick for that run is 10 AWG, which we are not linking until a checked in-stock listing exists.

    View on Amazon

12 AWG beats 14 on long 15 A runs

A 14 AWG cord is not “wrong” at 25 feet. At 50–100 feet the same 15 A saw is a voltage-drop problem. Read 12 vs 14 gauge.

SJTW is a jacket, not a gauge

Outdoor-rated means weather-resistant insulation. It does not make 16 AWG safe for a saw. See outdoor / SJTW.

100 feet wants thicker copper

Two cheap 50-foot 16 AWG cords in a daisy chain are how tools overheat. Use the 100-foot gauge guide.

Guides

Bookmark the page that matches the decision you are actually making — not a doorway list of every cord on the shelf.