Calculation Methodology & Technical Standards

How MarineWireCalc ensures accuracy, electrical safety, and consistency across all tools.

1. The ABYC E-11 Standard

MarineWireCalc's DC Wire Gauge and Voltage Drop calculators are built directly on the standards formulated by the American Boat and Yacht Council (ABYC), specifically standard E-11: AC and DC Electrical Systems on Boats.

2. Circular Mils and Conductor Resistance Formula

Cable thickness is calculated using the standard electrical engineering Circular Mils (CM) formula:

• K (Resistance factor): Fixed at 10.75, representing the specific resistance of tinned marine copper conductors operating at 75°C.
• I (Current in Amperes): The continuous maximum electrical load of the appliance.
• L (Total circuit length): Total conductor length from source to device and back to ground/negative terminal in feet.
• E (Allowable voltage drop): 3% for critical safety systems (trolling motors, electronics) or 10% for non-critical loads (cabin lighting).

3. Non-Linear Trolling Motor Throttle Curves

Unlike simple resistive heating elements, electric trolling motors use pulse-width modulated (PWM) or stepped-resistance speed controllers. Amperage draw does not increase linearly:

This exponential curve accurately models real-world conditions where Speed 1–2 draws minimal current, while Speed 5 (WOT) draws maximum full-rated current.