What Gauge Wire for 20 Amps?
20 amp circuits handle moderate loads like inverters, larger DC appliances, and multiple devices. At 12V, 20 amps delivers 240 watts. Proper wire sizing prevents voltage drop and heat buildup.
10ft Run
12 AWG
25ft Run
10 AWG
50ft Run
8 AWG
100ft Run
6 AWG
* Based on 12V DC with 3% voltage drop limit. AC circuits may use smaller wire.
Wire Gauge Calculator
Round trip: 50ft (distance x 2)
Recommended Wire Gauge
4 AWG
For 20A at 25ft (12V, 3% max drop)
Power
240W
Actual Voltage Drop
2.1%
(0.26V)
Alternative Gauges
Fuse Recommendation
Use a 25A fuse (125% of rated current, rounded to standard size)
* Always verify with local electrical codes. This calculator is for reference only.
Complete Wire Gauge Chart (12V DC, 3% Drop)
| Wire Gauge | Max Amps @ 10ft | Max Amps @ 25ft | Max Amps @ 50ft | Max Amps @ 100ft |
|---|---|---|---|---|
| 18 AWG | 5A | 2A | 1A | 0.5A |
| 16 AWG | 8A | 3A | 2A | 1A |
| 14 AWG | 12A | 5A | 3A | 1A |
| 12 AWG | 20A | 8A | 4A | 2A |
| 10 AWG | 30A | 12A | 6A | 3A |
| 8 AWG | 50A | 20A | 10A | 5A |
| 6 AWG | 75A | 30A | 15A | 8A |
| 4 AWG | 120A | 48A | 24A | 12A |
| 2 AWG | 190A | 75A | 38A | 19A |
| 1/0 AWG | 300A | 120A | 60A | 30A |
| 2/0 AWG | 380A | 150A | 75A | 38A |
| 4/0 AWG | 600A | 240A | 120A | 60A |
* Round trip distance (double the one-way distance) is used in calculations.
Common Uses for 20A Circuits
- •Small inverters (200-300W)
- •Portable coolers/fridges
- •Large DC fans
- •Amateur radio equipment
- •Multiple lighting circuits combined
Wire Sizing Tips
- •12 AWG is the minimum for 20A, but only for short runs
- •For battery-to-inverter runs, keep distance under 6ft if possible
- •Use crimp ring terminals, not twist-on connectors for DC
- •Consider marine-grade wire for durability in harsh environments
- •Install a 25A fuse at the battery for 20A circuits
Key Considerations
- ⚠Battery cable runs should be as short as possible
- ⚠Use properly rated disconnect switches or breakers
- ⚠Voltage drop over 3% noticeably affects device performance
Frequently Asked Questions
What gauge wire for 20 amps at 12V?
12 AWG handles 20 amps for runs under 10ft. For 25ft, use 10 AWG. For 50ft, use 8 AWG. Low-voltage DC requires heavier wire than 120V AC at the same amperage.
Can 14 AWG handle 20 amps?
No. 14 AWG is rated for only 15A maximum and will overheat at 20A. Always use at least 12 AWG for 20A circuits, and heavier for longer runs.
Why does 12V need heavier wire than 120V?
At lower voltage, more current flows for the same wattage (Watts = Volts x Amps). A 240W load at 12V draws 20A, but at 120V only 2A. Higher current needs heavier wire.