Calculate wire gauge (AWG), maximum current capacity, or voltage drop for electrical wiring. Free online electrical engineering calculator with support for copper and aluminum wires.
Calculate wire gauge (AWG), current capacity, or voltage drop for electrical wiring
Formula:
R = (ρ × L × 2) / A, V_drop = I × R
Note: Length is for one-way distance. Calculator uses round-trip (×2) for resistance.
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Proper wire sizing is critical for electrical safety, efficiency, and code compliance. Whether you're designing electrical circuits, installing wiring, or troubleshooting voltage drop issues, understanding wire gauge calculations is essential. Our Wire Size Calculator makes it easy to determine the appropriate American Wire Gauge (AWG) size, calculate maximum current capacity, or determine voltage drop for electrical installations.
Wire size directly affects electrical resistance, current-carrying capacity, and voltage drop. Using undersized wires can lead to overheating, fire hazards, and excessive voltage drop that affects equipment performance. Our calculator helps ensure you select the correct wire size for your specific application.
Our Wire Size Calculator offers three different calculation modes:
Select your calculation mode, choose wire material (copper or aluminum), enter the known values, and click Calculate to get instant results with detailed step-by-step solutions.
Wire size calculations are based on electrical resistance and Ohm's law:
R = (ρ × L × 2) / A
Where: R = resistance, ρ = resistivity, L = length, A = cross-sectional area
Note: Length is multiplied by 2 for round-trip (out and back)
V_drop = I × R
Where: V_drop = voltage drop, I = current, R = resistance
AWG is a standardized wire gauge system used in North America. Lower AWG numbers indicate larger wire diameters:
Wire size calculations are essential in numerous electrical applications:
It's crucial to use consistent units in your wire size calculations:
Tip: Our calculator automatically handles unit conversions for length. The calculator uses round-trip distance (length × 2) for resistance calculations, which is standard practice for voltage drop calculations.
A 120V circuit needs to carry 20A over 50 feet with a maximum 3% voltage drop. What wire size is needed?
Maximum voltage drop: 120V × 0.03 = 3.6V
Required resistance: R = 3.6V / 20A = 0.18 Ω
Required area: A = (1.68×10⁻⁸ Ω·m × 15.24 m × 2) / 0.18 Ω ≈ 2.85 mm²
Result: 12 AWG wire (3.31 mm²) is required
What is the maximum current for 14 AWG copper wire over 100 feet with a 3% voltage drop at 120V?
14 AWG area: 2.08 mm²
Resistance: R = (1.68×10⁻⁸ × 30.48 m × 2) / (2.08×10⁻⁶ m²) ≈ 0.49 Ω
Maximum current: I = 3.6V / 0.49 Ω ≈ 7.3 A
What is the voltage drop for 16 AWG copper wire carrying 5A over 25 feet at 12V?
16 AWG area: 1.31 mm²
Resistance: R = (1.68×10⁻⁸ × 7.62 m × 2) / (1.31×10⁻⁶ m²) ≈ 0.20 Ω
Voltage drop: V_drop = 5A × 0.20 Ω = 1.0 V (8.3%)
The choice between copper and aluminum wires affects calculations:
Aluminum wire typically requires one or two AWG sizes larger than copper for the same current capacity. Always use the correct material resistivity in your calculations.
Acceptable voltage drop depends on the application:
Excessive voltage drop can cause equipment malfunction, reduced efficiency, and safety issues. Always consult local electrical codes for specific requirements.
AWG (American Wire Gauge) is a standardized system for measuring wire diameter. Lower AWG numbers indicate larger wire diameters. For example, 12 AWG is larger than 14 AWG. The system is logarithmic, so each 3-gauge decrease doubles the cross-sectional area and current-carrying capacity.
Copper has better conductivity (lower resistance) but is more expensive. Aluminum is lighter and less expensive but requires larger gauge for the same current. Copper is more common in residential applications, while aluminum is often used in large commercial and industrial installations. Always use the correct material in calculations.
Acceptable voltage drop depends on the application. For branch circuits, 3% is typically the maximum. For feeders, 2% is common. Combined feeder and branch circuits should typically not exceed 5% total voltage drop. Always consult local electrical codes for specific requirements.
Wire length is multiplied by 2 because electrical current flows from the source to the load and back (round trip). The total resistance includes both the outgoing wire and the return wire, so we use 2× the one-way distance for accurate voltage drop calculations.
This calculator works for DC circuits and AC circuits with resistive loads. For AC circuits with inductive or capacitive loads, additional factors (power factor, skin effect) may need consideration. For most residential and commercial applications, this calculator provides accurate results.
Always consult local electrical codes and safety standards. This calculator provides theoretical values. In practice, consider: ambient temperature, wire bundling, installation method, and safety margins. When in doubt, consult a licensed electrician or electrical engineer.
Proper wire sizing is essential for electrical safety, efficiency, and code compliance. Our Wire Size Calculator simplifies these calculations, making it easy to determine appropriate wire gauge, current capacity, and voltage drop for electrical installations.
Ready to explore more electrical concepts? Check out our other calculators like the Watt Calculator for power calculations, or the Frequency Calculator for wave frequency analysis that often complements electrical engineering work.
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