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Copper wire for 48V system, 25ft one-way run
Assumes 60 °C terminals, 30 °C air, 3 or fewer wires together. Hot spaces, bundled wires and long-running loads need thicker wire. Check your local code edition with your inspector. Electrical work can kill or seriously injure you and start fires. Consult a licensed electrician or other qualified professional.
Assumes: Sized for 50 A, which is 1.25 × the current you entered
Safety and terms| Size | AWG | V Drop | Drop % | Status | Table ampacity | Power Loss | Est. Cost |
|---|---|---|---|---|---|---|---|
| 4 One size up | 0.6V | 1.3% | Passes | 70A | 24.6W | $125.00 | |
| 6 Recommended | 1.0V | 2.0% | Passes | 55A | 39.3W | $87.50 | |
| 8 One size down | 1.6V | 3.2% | Fails | 40A | 62.2W | $52.50 |
Actual wire sizes
Circles represent actual wire diameter. Place a ruler on your screen to verify. (Accuracy depends on your display's DPI settings)
Understanding the results
- Voltage Drop: Energy lost as heat in the wire. Lower is better.
- Table ampacity: Table ampacity at 60 °C, before derating.
- Power Loss: Watts wasted as heat. Larger wire = less loss.
- Wire Size: Visual circles represent actual physical diameter at 96 CSS pixels per inch. For best accuracy, ensure browser zoom is at 100% and your OS display scaling matches your monitor's actual PPI.
Wire size reference tables
Reference tables for wire sizing based on NEC (National Electrical Code) standards. These tables are provided for quick lookup when you already know your requirements.
Wire ampacity (NEC Table 310.16)
Table ampacity at 30°C air, before any derating, for the 60°C and 75°C columns. 14, 12 and 10 AWG also have a fuse or breaker cap under NEC 240.4(D), shown in the notes.
| AWG Size | Copper 60°C (A) | Copper 75°C (A) | Aluminum 60°C (A) | Aluminum 75°C (A) | Notes |
|---|---|---|---|---|---|
| 4/0 | 195 | 230 | 150 | 180 | |
| 3/0 | 165 | 200 | 130 | 155 | |
| 2/0 | 145 | 175 | 115 | 135 | |
| 1/0 | 125 | 150 | 100 | 120 | |
| 1 | 110 | 130 | 85 | 100 | |
| 2 | 95 | 115 | 75 | 90 | |
| 3 | 85 | 100 | 65 | 75 | |
| 4 | 70 | 85 | 55 | 65 | |
| 6 | 55 | 65 | 40 | 50 | |
| 8 | 40 | 50 | 35 | 40 | |
| 10 | 30 | 35 | 25 | 30 | NEC 240.4(D) caps the fuse or breaker at 30 A (Cu), 25 A (Al) |
| 12 | 20 | 25 | 15 | 20 | NEC 240.4(D) caps the fuse or breaker at 20 A (Cu), 15 A (Al) |
| 14 | 15 | 20 | — | — | NEC 240.4(D) caps the fuse or breaker at 15 A |
Source: NEC Table 310.16 (60°C and 75°C columns). 16 AWG and smaller are not shown: they are not used for power runs.
AWG wire diameter (ASTM B258)
Standard conductor diameters per American Wire Gauge. Overall diameters include typical THHN/THWN insulation.
| AWG Size | Conductor Diameter | Overall Diameter |
|---|---|---|
| 26 | 0.0159" (0.40 mm) | 0.050" (1.27 mm) |
| 25 | 0.0179" (0.45 mm) | 0.053" (1.35 mm) |
| 24 | 0.0201" (0.51 mm) | 0.056" (1.42 mm) |
| 23 | 0.0226" (0.57 mm) | 0.059" (1.50 mm) |
| 22 | 0.0254" (0.65 mm) | 0.058" (1.47 mm) |
| 21 | 0.0285" (0.72 mm) | 0.067" (1.70 mm) |
| 20 | 0.0320" (0.81 mm) | 0.068" (1.73 mm) |
| 19 | 0.0359" (0.91 mm) | 0.076" (1.93 mm) |
| 18 | 0.0403" (1.02 mm) | 0.078" (1.98 mm) |
| 17 | 0.0453" (1.15 mm) | 0.087" (2.21 mm) |
| 16 | 0.0508" (1.29 mm) | 0.092" (2.34 mm) |
| 15 | 0.0571" (1.45 mm) | 0.101" (2.57 mm) |
| 14 | 0.0641" (1.63 mm) | 0.109" (2.77 mm) |
| 13 | 0.0720" (1.83 mm) | 0.119" (3.02 mm) |
| 12 | 0.0808" (2.05 mm) | 0.128" (3.25 mm) |
| 11 | 0.0907" (2.30 mm) | 0.136" (3.45 mm) |
| 10 | 0.1019" (2.59 mm) | 0.148" (3.76 mm) |
| 9 | 0.1144" (2.91 mm) | 0.173" (4.39 mm) |
| 8 | 0.1285" (3.26 mm) | 0.188" (4.78 mm) |
| 7 | 0.1443" (3.67 mm) | 0.209" (5.31 mm) |
| 6 | 0.1620" (4.11 mm) | 0.225" (5.71 mm) |
| 5 | 0.1819" (4.62 mm) | 0.247" (6.27 mm) |
| 4 | 0.2043" (5.19 mm) | 0.271" (6.88 mm) |
| 3 | 0.2294" (5.83 mm) | 0.296" (7.52 mm) |
| 2 | 0.2576" (6.54 mm) | 0.328" (8.33 mm) |
| 1 | 0.2893" (7.35 mm) | 0.360" (9.14 mm) |
| 1/0 | 0.3249" (8.25 mm) | 0.403" (10.24 mm) |
| 2/0 | 0.3648" (9.27 mm) | 0.443" (11.25 mm) |
| 3/0 | 0.4096" (10.40 mm) | 0.490" (12.45 mm) |
| 4/0 | 0.4600" (11.68 mm) | 0.543" (13.79 mm) |
Source: ASTM B258 for conductor diameters. Overall diameters are approximate with typical THHN/THWN insulation.
Why does this table have more sizes?
This table includes all AWG sizes (including odd gauges like 5, 7, 9, 11, 13, 15 and small gauges 23-26) for reference purposes. However, odd gauge wires are rarely used for electrical power wiring. The NEC only specifies ampacity ratings for even-numbered gauges, which is why the Ampacity and Resistance tables above show fewer sizes. Odd gauges exist primarily for specialty applications like jewelry, electronics, and tensile/structural uses where current capacity isn't the primary concern.
Wire resistance (NEC Chapter 9 Table 8)
DC resistance of stranded conductors at 75°C, in Ohms per 1000 feet. Used for voltage drop calculations.
| AWG Size | Copper (Ω/kft) | Aluminum (Ω/kft) |
|---|---|---|
| 4/0 | 0.0608 | 0.1 |
| 3/0 | 0.0766 | 0.126 |
| 2/0 | 0.0967 | 0.159 |
| 1/0 | 0.122 | 0.201 |
| 1 | 0.154 | 0.253 |
| 2 | 0.194 | 0.319 |
| 3 | 0.245 | 0.403 |
| 4 | 0.308 | 0.508 |
| 6 | 0.491 | 0.808 |
| 8 | 0.778 | 1.28 |
| 10 | 1.24 | 2.04 |
| 12 | 1.98 | 3.25 |
| 14 | 3.14 | 5.17 |
| 16 | 4.016 | |
| 18 | 6.385 | |
| 20 | 10.15 | |
| 22 | 16.14 |
Source: NEC 2023 Chapter 9 Table 8, stranded conductors.
Voltage drop formula
The standard formula for calculating voltage drop in DC circuits and single-phase AC circuits.
Where:
- Vdrop = Voltage drop (volts)
- L = One-way wire length (feet)
- I = Current (amps)
- R = Resistance (Ω per 1000 ft from table above)
- 2 = Factor for round-trip (positive and negative conductors)
Recommended maximum voltage drop:
- 3% for branch circuits (NEC recommendation)
- 5% total for feeder + branch combined
- 2-3% for solar/battery systems (efficiency)
Common wire size applications
Typical residential and solar applications for each wire size (copper conductors).
| AWG | Max Breaker | Common Applications |
|---|---|---|
| 14 | 15A | Lighting circuits, general-purpose outlets |
| 12 | 20A | Kitchen outlets, bathroom outlets, outdoor circuits |
| 10 | 30A | Dryers, water heaters, small AC units |
| 8 | 50A | Ranges, large AC units, EV chargers (Level 2) |
| 6 | 65A | Subpanels, large appliances, hot tubs |
| 4 | 85A | Subpanels, service entrance conductors |
| 2 | 115A | 100A subpanels, large solar inverters |
| 1/0 | 150A | 150A service entrance, battery bank connections |
| 4/0 | 230A | 200A service entrance, large battery systems |
Note: Actual wire size requirements depend on circuit length, ambient temperature, and conduit fill. Always verify with local codes.
