Wire Gauge Calculator
Calculate the correct wire gauge (AWG) for your electrical project. Enter amperage, distance, and voltage to determine safe wire sizing with voltage drop calculations.
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How to Use This Calculator
Selecting the correct wire gauge is critical for electrical safety. Our calculator helps you determine the right wire size based on your specific requirements:
- Enter the amperage (current) of your circuit - this is typically determined by your breaker size or the equipment you're powering.
- Input the one-way distance from the power source to the load in feet.
- Select your voltage (120V for standard household, 240V for large appliances, or other common voltages).
- Choose between single-phase and three-phase power systems.
- Click 'Calculate' to see the recommended wire gauge and voltage drop percentage.
Why This Matters
Using the wrong wire gauge isn't just an inconvenience - it's a serious safety hazard. Undersized wire can overheat, potentially causing fires, damaging equipment, or creating shock hazards. Oversized wire wastes money on materials. Additionally, excessive voltage drop over long runs can cause equipment to malfunction, lights to dim, and motors to run inefficiently or overheat. This calculator helps you find the balance between safety, performance, and cost.
- Prevent electrical fires by ensuring wire can handle the current safely
- Avoid voltage drop issues that cause equipment malfunction or inefficiency
- Save money by not over-specifying wire size unnecessarily
- Meet National Electrical Code (NEC) requirements for your installation
- Properly size wire for long runs where voltage drop becomes significant
Worked Examples
Shop Subpanel
You're running a 60-amp subpanel to a detached workshop 100 feet from your main panel at 240V single-phase.
Outdoor Lighting
Installing landscape lighting with a 15-amp circuit running 150 feet from the panel at 120V.
EV Charger
Installing a 50-amp Level 2 EV charger in your garage, 30 feet from the panel at 240V.
Common Mistakes to Avoid
- Using the breaker rating instead of actual load for calculations - always size for the breaker/circuit protection, not expected usage.
- Forgetting that NEC requires voltage drop under 3% for feeders and 5% total for branch circuits.
- Not accounting for round-trip distance in voltage drop - the calculator handles this, but manual calculations often miss it.
- Using aluminum wire ampacity ratings for copper wire - they're different, and aluminum requires larger gauges.
- Ignoring ambient temperature derating in hot locations like attics - this can require upsizing wire significantly.