ALARMING USA · SECURITY TOOLS

Voltage Drop Calculator

Estimate DC cable voltage loss for access control, alarms, cameras, and low-voltage security equipment.

System & Cable Settings

Supply Voltage

Custom Supply (V)

Copper Wire Gauge

One-Way Cable Distance (ft)

Total Load Current (A)

Include all loads on this circuit.

Minimum Device Voltage (V)

Use equipment manufacturer's rating.

Design Drop Limit (%)

Conductor Material

Calculated Results

Voltage at Device—

Voltage Drop—

Voltage Drop %—

Round-Trip Cable Resistance—

Load Power at Supply—

Estimated Cable Loss—

Enter your circuit details.

Voltage deliveredVoltage lost

Calculations assume a two-conductor DC circuit with a return path, constant current, and approximate conductor resistance at 20°C (68°F). Actual voltage loss may increase with temperature, connections, and installation conditions.

How to Use These Results

Enter the power supply output voltage, wire size, one-way distance to the device, and expected circuit current. The calculator accounts for both outgoing and return conductors (twice the one-way cable distance). Compare the estimated voltage at the equipment with its published operating range, and confirm the drop meets your project requirements. This is a planning estimate, not a substitute for manufacturer documentation, applicable codes, or engineered fire alarm design.