Free battery calculators

Small browser-only calculators for runtime, charging time, charge speed, health percentage, and drain rate. Every result is an estimate, not a hidden hardware reading.

Phone battery drain rate calculator

Calculate percentage points used per hour and a simple 100-to-0 runtime projection.

Battery health percentage calculator

Calculate full-charge capacity as a percentage of design capacity.

Phone battery runtime estimator

Estimate runtime from battery capacity in mAh and average current draw in mA.

Phone charge speed calculator

Calculate percentage points gained per hour from two battery readings and elapsed minutes.

Phone charging time estimator

Estimate charge time from capacity, charging current, start percentage, end percentage, and efficiency.