Wire Gauge Chart
In the workshopSize, ohms, ampacity, V-drop
Store name: “Wire Gauge Chart: AWG”
Coming soon
Not out yet — but it’s close.
Wire Gauge Chart: AWG is the wire table without the ad-swamped web page around it: every American Wire Gauge size from 4/0 to 40, the numbers you actu
- 254 original, FAA-cited practice questions
- All 12 ACS General subject areas
- Timed 60-question exam simulator, 42 to pass
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Free web tool
How do you calculate voltage drop and pick a wire gauge (AWG)?
For a two-wire run, voltage drop = 2 × current (A) × one-way length (ft) × the conductor's resistance per foot, where resistance per foot is ρ ÷ area in circular mils (ρ = 10.371 Ω·cmil/ft for copper, 17.0 for aluminum, adjusted for temperature). Divide the drop by the system voltage for the percentage; the common NEC guideline (an informational note, not a code rule) is to keep it at or under 3% on a branch circuit and 5% total including feeders. To cut the drop, step up a size — a lower AWG number is a fatter wire with less resistance — switch from aluminum to copper, or shorten the run. Wire gauge itself follows the ASTM B258 formula (diameter in mils = 5 × 92^((36 − n) ÷ 39)), so 10 AWG is 0.1019″ (2.588 mm) and every 3 gauges roughly doubles the cross-sectional area.
Conductor
12 AWG: 2.1 mm (80.8 mils) · 6,530 cmil (3.31 mm²) · ≈ 4 mm² IEC
Load & run
Target voltage drop
NEC informational note (not a rule): ≤3% on a branch circuit, ≤5% total including feeders.
Voltage drop over the round trip
2.38V
Longest run at 3%
75.6 ft
12 AWG Copper · 15 A · 120 V
DC resistance
1.588 Ω
per 1,000 ft · 5.211 Ω/km · Copper at 20 °C
NEC 310.16 ampacity — 12 AWG copper
60 °C
20 A
75 °C
25 A
90 °C
30 A
240.4(D) overcurrent cap: 20 A — the practical breaker limit for 12 AWG on most branch circuits.
Copper, insulated, ≤3 current-carrying conductors in raceway, cable or earth, 30 °C ambient.
Geometry and resistance are computed from the ASTM B258 AWG formula (ρ Cu 10.371, Al 17.0 Ω·cmil/ft at 20 °C); the 3% figure is a design guideline, not a code limit. Ampacity figures are typical NEC 310.16 reference values — the same engine as the app. Typical NEC Table 310.16 values for reference only. Actual ampacity depends on conditions, derating, terminations and local code — consult a licensed electrician and the current NEC before sizing conductors. NEC 240.4(D) caps overcurrent protection for small conductors: 14 AWG → 15 A, 12 AWG → 20 A, 10 AWG → 30 A, regardless of the table column.
Take it with you
The full Wire Gauge Chart app carries the whole 4/0–40 AWG chart with diameter, area, resistance, and weight for both copper and aluminum, the NEC 310.16 and hobby ampacity tables, a metric (mm²) cross-reference, and reverse gauge-from-measurement lookups — all one-tap and fully offline on your phone.
Coming soon to the App Store
What it is
The American Wire Gauge table as an app: every size from 4/0 to 40 with diameter, cross-section, resistance, weight, and typical ampacity, plus a voltage-drop calculator that works both directions — how much you lose, or how far you can run.
Why we built it
Look up "12 AWG diameter" or "voltage drop 10 gauge 50 ft" and you get a blurry chart buried in ads. Electricians, solar and automotive installers, and hobbyists need those numbers at the panel and the bench, often with no signal. Wire Gauge Chart puts the whole reference one tap deep, offline, with ampacity figures honestly labeled and disclaimed.
Want one like this?
Wire Gauge Chart is one of 92. We can build yours.
Every app on the shelf started as one honest problem, scoped small and built native, end to end. That’s exactly how we approach client work — designed, built and shipped, without the bloat.
