# Wire Size Calculator

> Calculate the correct wire gauge (AWG) based on current, voltage drop, and distance

**Category:** Conversion
**Keywords:** wire, gauge, AWG, electrical, amperage, amps, voltage drop, cable, conductor, copper, aluminum, current, wiring, electrical wire
**URL:** https://complete.tools/wire-size-calculator

## How it calculates

The calculation of wire gauge is based on the formula for voltage drop: Voltage Drop (V_d) = (2 × Length × Current × Resistivity) ÷ 1000. In this formula, 'Length' is the one-way distance of the wire in feet, 'Current' is the electrical load in amperes, and 'Resistivity' is a constant that represents the material's resistance (for copper, this is approximately 10.4 ohms per mil-foot). The factor of 2 accounts for the return path of the current. The resulting voltage drop can then be compared to the allowable voltage drop to determine the appropriate wire size according to the American Wire Gauge standard. The relationship is such that as the wire length or current increases, the required wire gauge size also increases to maintain efficiency and safety.

## Who should use this

Electricians determining wire sizes for residential wiring projects, electrical engineers designing circuits for industrial machinery, and renewable energy technicians evaluating wire needs for solar panel installations are specific use cases for this tool.

## Worked examples

Example 1: For a circuit carrying 20 amperes over a distance of 100 feet with a maximum allowable voltage drop of 3 volts. Using the formula: V_d = (2 × Length × Current × Resistivity) ÷ 1000, we can substitute: V_d = (2 × 100 × 20 × 10.4) ÷ 1000 = 41.6 volts. The calculated voltage drop exceeds the allowable drop, indicating a larger gauge wire is necessary. 

Example 2: For a 15 amp load over 50 feet to achieve a voltage drop of 2 volts. Applying the formula: V_d = (2 × 50 × 15 × 10.4) ÷ 1000 = 15.6 volts. Here, a smaller gauge wire is sufficient to keep the voltage drop within limits, suggesting a 14 AWG wire may be appropriate.

## Limitations

The Wire Size Calculator has specific limitations, including: 1) The calculator assumes a constant resistivity value for copper, which may vary with temperature; 2) It does not account for additional factors such as ambient temperature or insulation type that could affect voltage drop; 3) The tool assumes a linear voltage drop over the length, which may not be accurate in all scenarios; 4) It may not account for multi-wire configurations where derating may be required; 5) The calculations are based on ideal conditions and may not reflect real-world variations in installation.

## FAQs

**Q:** How does wire gauge affect electrical performance?


**A:** Wire gauge impacts the resistance of the wire, with smaller gauges having lower resistance, thereby reducing voltage drop and heat generation at higher currents.


**Q:** Can I use a wire gauge that is larger than required?


**A:** While using a larger gauge wire is generally safe, it may be impractical and more expensive, and could lead to increased difficulty in handling and installation.


**Q:** What factors should be considered in addition to current and distance?


**A:** Other factors include ambient temperature, insulation type, and the specific application requirements, which can all influence the choice of wire gauge.


**Q:** How do I determine the allowable voltage drop for my application?


**A:** Allowable voltage drop typically depends on the type of load and application; for general lighting, a 3-5% drop is common, while for sensitive equipment, a 1-3% drop is preferred.

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