Use this electronics calculation for a first-pass component, converter, signal, motor, or sensor estimate when the stated operating conditions and units match the device data.

Coil (V) (V)

Required number input.

Coil Resistance (Ω) (Ω)

Required number input.

Calculate DC relay-coil electrical power as applied voltage squared divided by coil resistance; AC impedance is outside this model. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Coil Power (W) (W)

The resulting coil power (w) returned as a number.

• Relay timing, coil power, inductance, and bounce depend on coil voltage, temperature, driver, suppression network, mechanical load, contact material, current, and aging. Contact ratings differ for AC, DC, resistive, inductive, and inrush loads.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check the result against the current datasheet and worst-case operating corners, then verify the circuit or measurement with simulation and bench testing where failure matters.

• Contactor Coil Current

  Calculate DC contactor-coil steady current from applied voltage and DC coil resistance; do not use this for AC inrush or inductive impedance.

• Motor Starting Current

  Estimate DC motor current at startup as applied armature voltage divided by winding resistance, before back EMF develops; drive current limiting is excluded.

• Dc Motor Armature Current

  Calculate DC motor armature current from applied voltage, back EMF, and winding resistance using the steady-state armature equation.