Wire Size Calculator: Right Gauge for AC, DC, Solar
Planning an electrical project and need a wire size calculator to ensure safety and efficiency? Whether it’s a 12V DC setup for off-grid solar or sizing wires for an air conditioner at 240V AC, choosing the correct wire gauge prevents overheating, voltage drops, and code violations. In 2025, with updated NEC guidelines emphasizing ampacity derating and 3% max voltage drop for low-voltage systems, accurate calculations are non-negotiable for DIYers, electricians, and installers. This guide covers wire size calculator AC, DC, solar, motor, and specialized tools like wire size calculator in mm2 or apps. Use our breakdowns and formulas to estimate sizes in AWG or mm², keeping projects compliant and performant.
How Does a Wire Size Calculator Work?
A wire size calculator DC or AC tool factors in load current (amps), voltage (e.g., 12V or 240V), one-way distance, allowable voltage drop (typically 3% for DC, 5% for AC), conductor material (copper vs. aluminum), and insulation type (e.g., THHN at 90°C). It outputs the minimum gauge based on ampacity (current-carrying capacity) and drop limits, per NEC Table 310.15(B)(16).
Key steps:
- Calculate amps: For DC, Amps = Watts / Volts; for motors/AC, use nameplate full-load current × 1.25 (NEC 80% rule).
- Check voltage drop: Drop % = (2 × Length × Amps × Resistance) / Voltage.
- Select gauge: Ensure ampacity ≥ calculated amps after derating (e.g., 80% for continuous loads >3 hours).
Pro tip: For wire size calculator app, mobile versions allow on-site inputs—ideal for solar or motor installs.
Basic Wire Size Formula
The core equation for DC wire size calculator (adaptable to AC with power factor ~1.0):
- Resistance (ohms/1000 ft) from NEC tables.
- Required Area (circular mils) = (2 × Length × Amps × 1000) / (Allowable Drop × Voltage).
- Convert to AWG/mm² using charts.
For simplicity: Use online equivalents of this for quick AWG results. Always verify with NEC for derating (ambient temp, bundling).
Average Wire Sizes by Application in 2025
Based on NEC 2023/2026 updates, here’s a snapshot for common scenarios (copper, 75°C insulation, 3% drop unless noted).
| Application |
Voltage/Amps Example |
Recommended Size (AWG) |
mm² Equivalent |
Notes |
| General DC (Lighting) |
12V, 10A, 50 ft |
14 AWG |
2.08 |
<3% drop; ampacity 20A. |
| AC Household |
240V, 15A, 100 ft |
14 AWG |
2.08 |
5% drop OK; 20A circuit. |
| Solar Panel Run |
48V, 20A, 30 ft |
10 AWG |
5.26 |
PV wire; UV-resistant. |
| Motor Starter |
240V, 10A (125% = 12.5A) |
12 AWG |
3.31 |
NEC 430; starting surge. |
| Air Conditioner (2-Ton) |
240V, 10.91A (×1.25=13.64A) |
12 AWG |
3.31 |
Nameplate MCA; 5% drop. |
For aluminum, upsize 2 AWG (e.g., 10 AWG copper = 8 AWG aluminum).
Wire Size Calculator for DC Systems: 12V Focus
Low-voltage DC wire size calculator prioritizes drop over ampacity due to high currents. For a 12 volt wire size calculator at 100W load (8.33A) over 20 ft:
- Drop limit: 3% (0.36V).
- Formula yields ~12 AWG (ampacity 25A, drop 2.5%).
| Load (Watts) |
Distance (ft) |
Size (AWG) |
mm² |
| 100 |
10 |
16 |
1.31 |
| 200 |
20 |
12 |
3.31 |
| 500 |
50 |
8 |
8.37 |
DC wire size calculator 12V apps factor battery charging voltage (14.4V) for accuracy.
AC Wire Size Calculator: 240V and Household
For wire size calculator AC 240V, focus on 5% drop and 125% continuous load. A 240V, 20A circuit (e.g., dryer) over 150 ft needs 6 AWG (drop 4.2%, ampacity 55A).
- Single-phase AC: Similar to DC but adjust for reactance (negligible for resistive loads).
- Motors: Multiply FLA by 1.25; e.g., 1HP motor at 10A → 12.5A, 14 AWG for short runs.
| Appliance |
Amps (Adjusted) |
Distance (ft) |
Size (AWG) |
| 240V Outlet |
20A |
50 |
12 |
| Range |
40A |
25 |
8 |
Solar and Renewable Wire Size Calculators
Solar wire size calculator or solar panel wire size calculator accounts for PV-specific NEC Article 690 (e.g., 1.56×Isc for ampacity). For a 300W panel (8A at 48V) to inverter 50 ft away: 10 AWG (2% drop).
| System Size |
Voltage |
Distance (ft) |
Size (AWG) |
Notes |
| 1kW Off-Grid |
12V |
30 |
6 |
High current; USE-2 wire. |
| 5kW Grid-Tie |
48V |
100 |
4 |
MC4 connectors; 1.25× drop factor. |
Use solar wire size calculator for temperature derating (e.g., +15% in hot climates).
Motor and Air Conditioner Wire Sizing
Motor wire size calculator: Per NEC 430, size at 125% FLA. A 3HP, 240V motor (14A FLA → 17.5A): 10 AWG for 50 ft (3% drop).
Air conditioner wire size calculator: Use MCA from unit nameplate. For 3-ton (18A MCA): 10 AWG copper.
| AC Tonnage |
MCA (Amps) |
Size (AWG, 100 ft) |
| 1.5 |
12.5 |
14 |
| 3 |
18 |
12 |
| 5 |
28 |
10 |
Wire Size in mm²: Metric Conversions
For international projects, a wire size calculator in mm2 converts AWG: 14 AWG ≈ 2 mm², 10 AWG ≈ 6 mm². IEC 60364 mirrors NEC for drops.
| AWG |
mm² |
Ampacity (Copper, 75°C) |
| 14 |
2.1 |
20A |
| 12 |
3.3 |
25A |
| 10 |
5.3 |
35A |
Tips for Using a Wire Size Calculator
- Always start with load calculations—use nameplates for motors/AC.
- Add 10-20% buffer for future loads.
- For apps like wire size calculator explorist, verify NEC compliance.
- Consult locals: NEC for US, IEC elsewhere.
- Oversize slightly for longevity—cheaper than fires.
Calculate Your Wire Size Now
Choosing the correct wire size is essential for safety and performance in any electrical system. Our Wire Size Calculator helps you find the right wire gauge based on voltage, current, length, and allowable voltage drop. Whether you’re working on residential, commercial, or industrial wiring, this tool ensures accuracy and compliance with electrical standards.
