How it works
Estimate charge time with a constant average power and efficiency. Real charging can taper; use average power rather than peak rating.
time = capacity × (target−start)/(power × efficiency)
Worked example
Show example inputs and result
Usable battery capacity: 60 · Starting charge: 20 · Target charge: 80 · Average charging power: 7 · Charging efficiency: 90.
- Charge time
- 5.71428571 h
Questions and answers
Why are some results rounded?
Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.
Are my inputs sent to a server?
The calculator processes inputs in your browser. Its code does not send your values to a server.
Method reviewed: October 8, 2026 · Methods & accuracy