August 16, 2026 Steven Eaton

Extension Cord Gauge Chart: AWG, Amps and Length (2026 Guide)

What gauge extension cord do you actually need?

Short answer: match the wire gauge to the amp draw of the tool and the length of the run. A 12 AWG cord carries a full 15-amp tool load out to 100 feet. A 14 AWG cord handles 15 amps only to about 50 feet, and a 16 AWG cord is a light-duty cord — lamps, chargers, and small loads over short runs. On a construction site, OSHA also requires the cord itself to be a three-wire type rated for hard or extra-hard usage under 29 CFR 1926.405(a)(2)(ii)(J).

This extension cord gauge chart exists because the number most people look at — the length printed on the package — is the least important one. What determines whether a cord can feed a circular saw without starving it is the copper cross-section, written as AWG (American Wire Gauge), where a smaller number means thicker wire. This page gives you the gauge-by-length-by-amps chart, the voltage-drop arithmetic behind it so you can verify any cell yourself, the jacket-code decoder for markings like SJTW, and the troubleshooting section for the most common field symptom: a cord that runs hot.

Why this matters.
An undersized extension cord does two things at once: it starves the tool of voltage, which makes universal motors run hot and die early, and it dissipates the lost power as heat in its own jacket — which is how cords buried under debris become ignition sources. On construction sites the stakes are regulatory as well: OSHA 29 CFR 1926.405 restricts what cords may be used and how, and 29 CFR 1926.404(b)(1) requires ground-fault protection for the receptacles that feed them.

Extension cord gauge chart: amps by wire size and cord length

The chart below combines two limits and always applies the stricter one: the cord set's own ampacity (what the copper and jacket are rated to carry continuously) and a 5% voltage-drop budget at 120 volts (the point past which motor tools start to suffer). Amp ratings for common cord sets are 13 A for 16 AWG, 15 A for 14 AWG, and 20 A for 12 AWG — but note that the standard household plug pattern (NEMA 5-15) caps any cord that carries it at 15 amps regardless of wire size.

Cord length	16 AWG	14 AWG	12 AWG	10 AWG
25 ft	13 A	15 A	15–20 A	20 A+
50 ft	10–12 A	15 A	15–20 A	20 A+
100 ft	6 A (light loads only)	~10 A	15 A	20 A
150 ft	Not recommended	~6 A	~10 A	15–16 A

The highlighted row is the one that decides most jobsite purchases: at 100 feet, 12 AWG is the thinnest wire that still delivers a full 15-amp saw load within the voltage-drop budget. That is why the 100-foot cords in our Extension cords and cord reels collection are 12-gauge — a 100-foot 16-gauge cord is a lamp cord that happens to be long.

The voltage-drop math, so you can check any cell yourself

None of the chart values above need to be taken on faith. Voltage drop in a copper cord is:

  VD (volts) = 2 × K × I × L ÷ CM

where K is copper's resistivity constant (about 12.9 ohm-circular-mil per foot at operating temperature), I is the current in amps, L is the one-way cord length in feet (the factor of 2 accounts for the round trip out and back), and CM is the conductor's cross-section in circular mils: roughly 2,583 for 16 AWG, 4,107 for 14 AWG, 6,530 for 12 AWG, and 10,380 for 10 AWG.

Worked through for the highlighted cell — a 15-amp tool on a 100-foot 12 AWG cord:

VD = 2 × 12.9 × 15 × 100 ÷ 6,530 ≈ 5.9 volts — 4.9% of 120 V, just inside the 5% budget.

Run the same 15 amps down a 100-foot 14 AWG cord and the drop is about 9.4 volts — nearly 8%, which is why the chart caps 14 AWG at roughly 10 amps for that length. A motor fed 8% low runs slower, pulls more current to do the same work, and heats both itself and the cord. This is the mechanism behind most burned-out saw motors blamed on the tool.

12/3 vs 14/3: what the numbers on the jacket mean

Cord shorthand like 12/3 reads as gauge-slash-conductor-count: 12 AWG copper, 3 conductors (hot, neutral, and the equipment grounding conductor). A 14/3 cord is the same three-wire construction in thinner 14 AWG copper. The practical difference between them:

Spec	12/3	14/3
Full 15 A load to	~100 ft	~50 ft
Typical cord-set rating	20 A (plug-limited to 15 A on NEMA 5-15)	15 A
Best use	Saws, compressors, heaters, any motor tool at distance	Drills, sanders, lights and medium loads on short runs
Weight and cost	Heavier, more copper, more expensive	Lighter and cheaper

If one cord has to do everything on a jobsite, buy 12/3. The premium over 14/3 is copper you will eventually need, and the failure mode of guessing wrong — a hot, voltage-starved cord — is invisible until it isn't. The second number matters too: on a construction site the "/3" is not optional, because OSHA requires extension cord sets used with portable tools to be of the three-wire type under 1926.405(a)(2)(ii)(J).

Jacket letters decoded: S, J, T, W, O and E

The letter string molded into the jacket — SJTW, SOOW, SJEOW — is a specification, not branding. Each letter answers one question:

Letter	Meaning	What it tells you
S	Service cord	Flexible cord rated 600 V; the hard-service family
J	Junior	300 V insulation instead of 600 V — "junior hard service." No J means the heavier 600 V build
T	Thermoplastic	Vinyl jacket — cheaper, stiffer in cold weather
O	Oil-resistant	One O: oil-resistant outer jacket. Two (OO): jacket and conductor insulation both
W	Weather-rated	Approved for outdoor use — sunlight- and moisture-resistant
E	Elastomer	Thermoplastic elastomer jacket — stays flexible in cold, common on premium cords

So SJTW — the most common jobsite marking, and the jacket on the outdoor extension cord waterproof 100 ft, black 12/3 SJTW in our lineup — reads: hard-service family, 300-volt junior class, thermoplastic jacket, weather-rated. The note to OSHA's construction wiring rule lists the S, ST, SO and STO types and their junior SJ, SJO, SJT and SJTO equivalents as examples of cords meeting the hard or extra-hard usage requirement.

Match the cord to the tool: typical nameplate draws

Amps, not watts, are what the chart runs on. Check the tool's own nameplate — it is stamped on every motor housing — and use these typical ranges only for planning:

7-1/4 in circular saw: 13–15 A — a 12 AWG cord at any length past 50 ft
Miter saw / table saw: 15 A — same rule, and keep the run as short as possible
Angle grinder (4-1/2 in): 6–11 A — 14 AWG to 50 ft, 12 AWG past that; see how to use an angle grinder safely for the rest of the setup
Corded drill: 5–8 A — 16 AWG is acceptable to 25 ft, 14 AWG beyond
Wet/dry vacuum: 8–12 A — the RIDGID RT1600 16-gallon wet/dry vacuum draws 11 A at full pull
Air compressor (pancake): 10–15 A running with a hard starting surge — 12 AWG minimum, short run, and never on a daisy-chain
LED area light: 0.5–2 A — any cord in the chart handles lighting; see the work lighting lineup

How to size a cord for any tool in four steps

Read the nameplate amps. Use the amp figure printed on the tool's motor plate, not a guess. If the plate shows only watts, divide by 120 to get amps.
Measure the real run. Pace the actual path the cord will take — around obstacles, up stairs — not the straight-line distance. Round up to the next standard length (25, 50, 100 ft).
Find the row and column. In the chart above, find the length row, then move right until the amp capacity meets or exceeds the nameplate figure. That column is your minimum gauge — thicker (lower AWG) is always acceptable.
Check the jacket and the ground pin. For jobsite use the marking must be a hard- or extra-hard-usage type (SJTW or better), the cord must be three-wire, and the ground pin must be intact — a cord with a snapped ground pin fails the daily visual inspection required under OSHA's assured equipment grounding program rules.

Why is my extension cord hot? The troubleshooting section

A warm cord after an hour of saw work is normal physics — some loss is unavoidable. A cord that is hot to the touch, or hot at one specific spot, is telling you something specific:

Hot along its whole length: the cord is undersized for the load. Check the nameplate against the chart — this is the classic 15-amp saw on a 100-foot 14 AWG cord. Swap to 12 AWG or shorten the run.
Hot at the plug or connector only: worn or loose contacts arcing inside the fitting. Replace the cord (or the tool plug); heat at a connection point is a pre-ignition symptom, not a nuisance.
Hot while coiled or on a reel: a coiled cord cannot shed heat — the loops insulate each other. Fully unwind any cord or jobsite power and electrical reel before running motor loads through it; reel manufacturers publish sharply lower amp ratings for the wound state.
Hot with two cords chained: the resistances add. A 50-foot and a 100-foot 14 AWG cord chained together are a 150-foot cord that can honestly deliver about 6 amps. Chaining also adds two more connector interfaces — the failure points from the previous bullet.
Breaker trips but the cord seems fine: voltage drop raises motor current draw. A tool that runs fine on 25 feet can trip a 15 A breaker on 150 feet because the starved motor pulls harder. The fix is more copper, not a bigger breaker.

Worked example: powering a chop station 90 feet from the panel

To make the workflow concrete, here is the sizing pass for a real setup — a 15-amp miter saw and an LED area light running 90 feet from a garage receptacle:

Add the loads. Miter saw nameplate 15 A; LED light 1.2 A. Peak concurrent draw ~16 A — over a 15 A circuit, so the light moves to a second cord or you accept that the saw's 15 A only occurs during cuts. Plan the cord for the 15 A saw.
Round the run up. 90 feet of walking path means a 100-foot cord.
Read the chart. The 100 ft row reaches 15 A only at 12 AWG. A 12/3 SJTW cord such as the 100 ft 12/3 outdoor extension cord waterproof, heavy duty power cord is the minimum spec — verify the drop: 2 × 12.9 × 15 × 100 ÷ 6,530 ≈ 5.9 V, inside the 5% budget.
Check protection. The receptacle feeding the cord needs GFCI protection on a construction site under 1926.404(b)(1)(ii); a lighted-end cord like the PlugSaf 100ft 12/3 outdoor extension cord waterproof with lighted end confirms power at the far end at a glance.
Route and inspect. Keep the cord out of walkways or protect it from damage, fully extended, ground pin intact, jacket unbroken — the daily-use checks that OSHA's construction wiring rules formalize.

The same arithmetic covers every cord in the extension cords and cord reels collection, and the generator-fed version of this setup — where cord sizing meets wattage math — is covered in how to run a generator safely and our jobsite generators lineup.

Frequently asked questions

What gauge extension cord do I need for a 15 amp tool?

12 AWG for any run past 50 feet; 14 AWG is acceptable to about 50 feet. At 100 feet, 12 AWG is the minimum that keeps voltage drop inside 5% at 15 amps — the arithmetic is 2 × 12.9 × 15 × 100 ÷ 6,530 ≈ 5.9 volts. Browse 12-gauge options in our extension cords and cord reels collection.

What gauge extension cord do I need for 100 feet?

12 AWG for tool loads (up to 15 A), 10 AWG if you need a full 20 A at that distance, and 14 AWG only for loads around 10 A or less. A 100-foot 16 AWG cord should be limited to about 6 amps — lighting and chargers, not motors.

Is 12/3 better than 14/3?

For jobsite use, yes — 12/3 carries a full 15-amp load twice as far (about 100 ft vs 50 ft) and runs cooler at any load. 14/3 remains a legitimate choice for short runs and medium loads where its lighter weight matters. If one cord must do everything, buy 12/3.

What does 12/3 mean on an extension cord?

12 AWG conductor gauge, 3 conductors: hot, neutral, and equipment ground. The three-wire construction is what carries the ground pin, and OSHA's construction standard requires extension cord sets used with portable tools to be of the three-wire type under 1926.405(a)(2)(ii)(J).

What does SJTW mean?

S = hard-service cord family, J = junior (300 V insulation class), T = thermoplastic jacket, W = weather-rated for outdoor use. SJTW is the standard jobsite cord marking; SJEOW substitutes a cold-flexible elastomer jacket with an oil-resistant outer layer.

How many watts can a 12 gauge extension cord handle?

At 120 volts, a 12 AWG cord's 15–20 amp capacity translates to roughly 1,800–2,400 watts, with the lower figure applying at 100 feet where voltage drop governs. Divide any tool's wattage by 120 to convert back to amps for the chart.

Can I daisy-chain two extension cords together?

Physics allows it; good practice and most site rules do not. The lengths add for voltage-drop purposes — two 50-foot 14 AWG cords equal one 100-foot cord capped near 10 amps — and every added connector pair is a wear point that heats under load. Buy the length you need instead.

Why does my extension cord get hot?

Whole-length heat means the wire is undersized for the amp draw; connector-only heat means worn or arcing contacts; heat while coiled means the loops are insulating each other. The first is fixed by the chart above, the second by replacement, the third by fully unwinding the cord before loading it.

Can I run a circular saw on a 100-foot extension cord?

Yes — on 12 AWG. A 13–15 amp saw at 100 feet sits right at the 5% voltage-drop limit on 12-gauge copper and well past it on 14-gauge. If the saw bogs in the cut or the cord warms noticeably, the run is too long for the gauge.

Do extension cords on a construction site need to be GFCI protected?

The receptacles feeding them do: OSHA 1926.404(b)(1)(ii) requires ground-fault circuit interrupters on 120-volt, 15- and 20-amp receptacles that are not part of a building's permanent wiring, with the alternative being a written assured equipment grounding conductor program with documented testing. Either way, a cord with a missing ground pin fails inspection.

Can a damaged extension cord be repaired with electrical tape?

Not on a jobsite. OSHA 1926.405(g)(2)(iii) requires flexible cords to be used in continuous lengths without splice, with one narrow exception: hard-service cords No. 12 AWG or larger may be spliced only if the splice restores the insulation, outer sheath properties and usage characteristics of the original cord — a standard tape wrap does none of that. A cord with damaged insulation gets replaced or professionally re-terminated.

What is the maximum length an extension cord can be?

No regulation sets a maximum length; voltage drop does. Every added foot costs voltage, so the practical ceiling is where your tool's amp draw crosses the 5% budget for the gauge — about 100 ft at 15 A on 12 AWG, about 150 ft at 15 A on 10 AWG. Past that, move the power source closer, which is the role of a jobsite generator or a portable power station.

Are indoor and outdoor extension cords different?

Yes — the W in the jacket code. Outdoor-rated cords carry sunlight- and moisture-resistant jackets; indoor cords may crack and degrade in UV and weather. Every cord in our jobsite lineup is W-rated, like the 12 gauge 100 ft heavy duty outdoor extension cord, waterproof.

Does a longer cord need a thicker wire even for the same load?

Yes. Resistance grows linearly with length, so the same 15-amp load that a 14 AWG cord feeds comfortably at 25 feet exceeds the voltage-drop budget at 100 feet. Length and gauge trade off directly — that is the entire logic of the chart.

What extension cord does a generator need?

Size it exactly like a wall-fed cord — nameplate amps and run length against the chart — but note the receptacle type: a generator's 30-amp outlet needs a 10 AWG cord with the matching locking plug to deliver its rating. Cord-and-generator pairing is covered in how to run a generator safely.

Why do jobsite cords have lighted ends?

The lighted plug confirms the cord is energized at the far end, which saves the walk back to the receptacle when a tool goes dead — the fault is downstream of a lit end, upstream of a dark one. It is a diagnostic feature, not a safety certification. Multi-outlet ends serve a related purpose: a three-outlet 12-gauge cord such as the 100 ft 12 gauge heavy duty extension cord with multiple outlets splits one run for a light and a charger without a second cord — keep the combined draw inside the chart's limit for the length, and reserve the full capacity when a saw is on the run, as with the single-outlet HUANCHAIN 12/3 gauge heavy duty outdoor extension cord.

Is a cord reel derated compared with the same cord loose?

Sharply. A wound cord cannot shed heat, so reel manufacturers publish two ratings — wound and fully extended — and the wound figure can be less than half. Unreel completely before running saws, heaters or compressors through a reel.