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 Resistance (Ω) (Ω)

Required number input.

Electrical Time Constant (s) (s)

Required number input.

Calculate relay-coil inductance from measured coil resistance and RL electrical time constant using L=Rτ; contact mechanics are not included. 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 Inductance (H) (H)

The resulting coil inductance (h) 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.

• Relay Coil Power

  Calculate DC relay-coil electrical power as applied voltage squared divided by coil resistance; AC impedance is outside this model.

• Relay Operate Time

  Estimate how long an RL relay coil takes to reach its pickup voltage from the L/R time constant.

• Supercapacitor RC Time Constant

  Calculate τ=RC for a supercapacitor and a series or load resistance. This ideal first-order time constant does not model voltage-dependent capacitance or leakage.