Wire Gauge Calculator (AWG)
Enter your circuit amps, one-way distance, and voltage — get the NEC-correct AWG wire size with full voltage drop calculation. Shows both the ampacity minimum and the voltage drop minimum so you always use the more conservative (safer) wire. Covers 14 AWG to 4/0 AWG, copper and aluminum, 120V through 480V. Based on NEC 2023 Table 310.16.
Advanced options — derating, breaker & conduit
Long run (50 ft) requires upsizing from 12 AWG to 10 AWG for voltage drop.
Copper vs Aluminum (for 20A at 50 ft on 120V)
Wire Gauge Page Library
The 10 promoted wire-gauge pages kept intentionally small, safety-polished, and aligned with the current sitemap.
Wire checks
Specific AWG checks with copper/aluminum assumptions, distance, voltage, ampacity, and voltage-drop context.
Circuit sizing examples
120V and 240V examples for common amperage and run-length questions.
Gauge comparisons
Safe comparison pages for adjacent gauges with clear NEC and local-code caveats.
Common presets
Carefully limited application presets for kitchen outlets and EV charger planning.
How to size a wire gauge (step by step)
Wire sizing requires satisfying two independent constraints:
- Ampacity: The wire must carry the load current without overheating. From NEC 2023 Table 310.16 — e.g., 12 AWG copper is rated 20A at 60°C.
- Voltage drop: NEC 215.2 recommends ≤ 3% for branch circuits. Formula:
VD = (2 × K × I × L) / CMwhere K = 12.9 (copper) or 21.2 (aluminum), I = amps, L = one-way feet, CM = circular mils.
Use the larger of the two minimum wire sizes. For short runs, ampacity governs. For long runs (100+ feet), voltage drop typically requires a larger wire.
NEC ampacity table (copper, in raceway)
| AWG | Cu 60°C | Cu 75°C | Al 75°C | Common use |
|---|---|---|---|---|
| 14 AWG | 15A | 20A | — | Lighting, 15A outlets |
| 12 AWG | 20A | 25A | 20A | Kitchen, bathroom, 20A outlets |
| 10 AWG | 30A | 35A | 30A | Dryer, water heater |
| 8 AWG | 40A | 50A | 40A | EV charger (Level 2), large AC |
| 6 AWG | 55A | 65A | 50A | Hot tub, 50A range, 60A AC |
| 4 AWG | 70A | 85A | 65A | Small subpanel, 70A circuits |
| 2 AWG | 95A | 115A | 90A | 100A service, subpanel feeder |
| 1/0 | 125A | 150A | 120A | 100A Al service entrance |
| 2/0 | 145A | 175A | 135A | 150A feeder, 200A Al sub |
| 3/0 | 165A | 200A | 155A | 200A service (common Al) |
| 4/0 | 195A | 230A | 180A | 200A copper service |
NEC 2023 Table 310.16. Not more than 3 current-carrying conductors in raceway, 30°C ambient.
Frequently asked questions
What wire gauge do I need for a 20A circuit?▾
12 AWG copper is the NEC minimum for a 20A circuit at 60°C. However, for runs over 50 feet at 120V, voltage drop may require 10 AWG to stay within the 3% NEC recommendation. Always check both ampacity AND voltage drop — this calculator does both automatically.
What wire for a 50A 240V electric range or EV charger?▾
For 50A at 240V for typical distances (under 50 ft), 6 AWG copper is the standard recommendation (65A ampacity at 75°C). For longer runs, 4 AWG may be needed for voltage drop. This calculator computes the exact minimum for your specific run length.
Can I use aluminum wire for a subpanel feeder?▾
Yes — aluminum is commonly used for service entrance conductors and subpanel feeders 10 AWG and larger, but NOT for branch circuit wiring in homes (fire risk at smaller gauges). Always use AL-rated lugs/breakers and apply anti-oxidant compound at connections. 3/0 aluminum is the most common 200A service entrance conductor.
What is the NEC rule for voltage drop?▾
NEC 215.2 is a recommendation (not a hard code requirement) that branch circuits should not exceed 3% voltage drop and feeders not exceed 2%, with a combined maximum of 5%. Many AHJs (building inspectors) enforce these as requirements. Our calculator flags violations automatically.
What does the 80% continuous load rule mean?▾
NEC 210.19 requires that branch circuits serving continuous loads (loads energized for 3 or more hours) be sized at 125% of the continuous load — or equivalently, the load must not exceed 80% of the wire's ampacity. For example, a 20A circuit can serve 16A continuous. This applies to EV chargers, commercial HVAC, commercial lighting, etc.
What is the difference between AWG and mm²?▾
AWG (American Wire Gauge) is the US standard. Europe uses mm² (cross-sectional area). Common equivalents: 14 AWG ≈ 2.5 mm², 12 AWG ≈ 4 mm², 10 AWG ≈ 6 mm², 8 AWG ≈ 10 mm², 6 AWG ≈ 16 mm², 4 AWG ≈ 25 mm², 2 AWG ≈ 35 mm². This calculator shows both units.