Ohm's Law Calculator

Calculate wire resistance based on AWG size, material, and length. Perfect for field calculations.

Formula: R = ρ × (L / A)
Where: ρ = resistivity, L = length, A = cross-sectional area

Wire AWG Size

Wire Material

Wire Length (Feet)

Wire Type

Calculate power loss in your circuit and determine efficiency. Critical for battery systems.

Formula: P_loss = I² × R
Efficiency: η = (1 - V_drop / V_source) × 100%

System Voltage (Volts)

Current Draw (Amps)

Wire Resistance (Ohms)

Calculate total current draw from power requirements using Ohm's Law: I = P / V

Formula: I_total = P_total / V
Where: I = current (Amps), P = power (Watts), V = voltage (Volts)

System Voltage

Total Power Required (Watts)

Equipment Power Draw

Determine proper fuse/breaker size per ABYC E-11 standards. Protects your wire, not your device.

⚠️ Important: The fuse must protect the WIRE, not the device. It must be ≤ wire ampacity.

Continuous Current Draw (Amps)

Wire AWG Size

Analyze complex circuits with series and parallel components.

Series: R_total = R1 + R2 + R3...
Parallel: 1/R_total = 1/R1 + 1/R2 + 1/R3...

Circuit Configuration

Supply Voltage (Volts)

Resistances (Ohms)

V = I × R
Voltage equals current multiplied by resistance. This is the foundation of all electrical calculations.

P = V × I
Power equals voltage multiplied by current. Understanding power helps prevent overloads.

The American Boat and Yacht Council (ABYC) E-11 standard ensures safe electrical systems on boats. Key principles: