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.

Capacity (mAh)

Rated charge capacity of the battery.

Load current (mA)

Constant current drawn by the load.

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. 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]

Runtime (h)

Estimated discharge time until the capacity is used up.

• 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.

• Battery Runtime Hours

  Compute battery runtime in hours as capacity in ampere-hours divided by load current in amperes.

• Capacity From Runtime

  Compute required battery capacity in ampere-hours as load current multiplied by runtime hours.

• Charge Current C-Rate

  Compute a safe constant-current charge rate for a battery from its capacity and a C-rate multiple.