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.

Measured (V) (V)

Required number input.

Empty (V) (V)

Required number input.

Full (V) (V)

Required number input.

Estimate fuel-gauge state of charge by linear interpolation between user-supplied empty and full open-circuit voltages; chemistry, load, and temperature can make this inaccurate. 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]

State Of Charge (%) (%)

The resulting state of charge (%) returned as a number.

• Battery capacity, state of charge, runtime, and aging depend on chemistry, temperature, discharge profile, cutoff voltage, cell balance, charge method, rate capability, self-discharge, and prior history. Nominal amp-hour or watt-hour ratings do not guarantee usable energy under every load.
• 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.

• Piezoelectric Open-Circuit Voltage

  Estimate open-circuit piezoelectric voltage as generated charge divided by effective capacitance. Loading, leakage, and amplifier input impedance can reduce measured voltage.

• Internal Resistance

  Estimate battery internal resistance from open-circuit voltage, loaded voltage, and load current.

• Battery Life Calculator

  Estimate battery runtime from rated charge capacity and constant load current: hours = mAh / mA. Real-world derating (Peukert effect, temperature, cutoff voltage) is not modeled.