- Enter the current — the load current in amps your circuit will carry.
- Enter the system voltage — 120V, 240V, 12V, 48V, etc.
- Enter the distance — one-way distance from the power source to the load in feet or meters.
- Select wire material — copper (lower resistance, higher cost) or aluminum (higher resistance, lower cost).
- Set maximum voltage drop — NEC recommends 3% for branch circuits and 5% for feeder circuits.
- Select phase — single phase (residential) or three phase (commercial/industrial).
- Click Calculate — view the recommended AWG gauge, actual voltage drop, voltage at the load, power loss, wire resistance, diameter, and area. The reference table highlights the recommended gauge.
Wire Gauge Calculator (AWG) — Find the Right Wire Size
Selecting the correct wire gauge is critical for electrical safety, efficiency, and code compliance. An undersized wire overheats and creates fire hazards, while an oversized wire wastes money. Our Wire Gauge Calculator determines the optimal AWG wire size based on your load current, system voltage, wire run distance, and acceptable voltage drop — all computed instantly in your browser with complete privacy.
Why Wire Sizing Matters
Every wire has electrical resistance that causes two problems: voltage drop (the load receives less voltage than the source provides) and heat generation (I²R losses that waste energy and can cause fires). The National Electrical Code (NEC) limits both ampacity (maximum safe current) and voltage drop to protect people and equipment.
Key Features
- 19 AWG Sizes: From 4/0 (heaviest, 230A) down to 26 AWG (lightest, 0.8A), covering residential, commercial, and electronics applications.
- Copper and Aluminum: Different resistivity values for both materials, so recommendations account for the material you plan to use.
- Single and Three Phase: Adjusts the wire run calculation factor — single phase uses 2× distance (round trip), three phase uses √3× distance.
- Voltage Drop Calculation: Shows the exact voltage drop in volts and as a percentage, plus the actual voltage delivered to the load.
- Power Loss: Calculates I²R losses in watts so you know how much energy is wasted as heat in the wiring.
- Wire Properties: Displays diameter (mm), cross-section area (mm²), and NEC 60°C ampacity for the recommended gauge.
- Reference Table: Complete AWG table with all 19 gauge sizes, highlighting the recommended gauge for easy identification.
- Calculation History: Saves past calculations in your browser for easy reference.
How the Calculation Works
Step 1: Determine Required Wire Resistance
The maximum allowable voltage drop determines the maximum wire resistance:
V_drop_max = V_system × (max_percent / 100)
R_max_per_km = V_drop_max / (I × L_roundtrip_km)
Where L_roundtrip = distance × 2 for single phase, or distance × √3 for three phase.
Step 2: Find the Smallest Sufficient Gauge
Starting from the smallest (thinnest) wire, the calculator finds the first gauge that satisfies both conditions:
- Wire resistance per km ≤ maximum allowable resistance per km
- Wire ampacity ≥ circuit current
Step 3: Calculate Actual Performance
Using the recommended wire's actual resistance, the calculator computes the real voltage drop, power loss, and delivered voltage.
AWG Size Reference
The American Wire Gauge system has an inverse relationship between gauge number and wire size:
- 4/0 AWG: 11.684mm diameter, 107.22mm², 230A — heavy service entrance, industrial feeders
- 2 AWG: 6.544mm diameter, 33.63mm², 115A — sub-panel feeders, heavy appliances
- 6 AWG: 4.115mm diameter, 13.30mm², 65A — large appliances, AC units, hot tubs
- 10 AWG: 2.588mm diameter, 5.26mm², 30A — dryers, water heaters, 30A circuits
- 12 AWG: 2.053mm diameter, 3.31mm², 20A — standard residential outlets and lighting
- 14 AWG: 1.628mm diameter, 2.08mm², 15A — lighting circuits, low-load outlets
- 18-22 AWG: Low-power applications — doorbells, thermostats, speakers, electronics
Voltage Drop Guidelines
The NEC recommends these maximum voltage drop limits:
- 3% for branch circuits (outlets, lights, appliances)
- 5% for feeder + branch circuit combined
- 2% for sensitive equipment (computers, medical devices)
Excessive voltage drop causes lights to dim, motors to run hot, and electronics to malfunction. In extreme cases, voltage drop can prevent equipment from starting at all.
Copper vs Aluminum
Copper wire has about 61% the resistance of aluminum wire of the same size, making it the better conductor. However, aluminum is significantly cheaper and lighter. For the same ampacity, aluminum wire needs to be approximately 2 AWG sizes larger than copper. Aluminum is commonly used for service entrance cables, utility feeders, and long outdoor runs where weight and cost are important factors.
Common Applications
- Residential 15A circuit: 14 AWG copper for short runs, 12 AWG for longer runs
- Residential 20A circuit: 12 AWG copper (standard for kitchens, bathrooms)
- Electric dryer/range: 10 AWG or 8 AWG copper for 30A or 40A circuits
- EV charger (50A): 6 AWG copper for distances under 50 feet
- Sub-panel feeder: 2 AWG or larger, often aluminum to save cost
- Solar panel runs: Sized for voltage drop over long outdoor distances
Privacy and Security
All calculations run entirely in your browser using JavaScript. Your circuit specifications are never transmitted to any server. No accounts, no tracking, no data collection.