EV Charging Time Calculator
Calculate how long it takes to charge an electric vehicle from a given state of charge to a target, given the charger power.
How to use this tool
- Enter the battery capacity in kWh.
- Enter your starting and target charge percentages.
- Enter the charger power in kW (check your charging equipment or vehicle display).
- The result shows energy needed and estimated charging time in hours.
Plan your EV charging session by estimating how long a charge will take.
Formula
Energy needed (kWh) = Battery capacity (kWh) × (Target % − Start %) ÷ 100
Charge time (h) = Energy needed (kWh) ÷ Charger power (kW)
How it works
This calculator determines EV charging duration by computing the kilowatt-hours required to fill the battery from the current state of charge to the target, then dividing that energy by the charger's rated power output.
The calculation assumes the charger delivers its full rated power throughout the session; in practice, DC fast chargers taper speed above 80% state of charge and AC chargers may be limited by the vehicle's onboard charger, so actual time may be longer.
Worked example
Worked example
- Charge needed: 80% − 20% = 60 percentage points
- Energy needed: 75 kWh × 60 ÷ 100 = 45.0 kWh
- Charge time: 45.0 kWh ÷ 7.2 kW = 6.25 hours
Charging a 75 kWh battery from 20% to 80% at 7.2 kW requires 45.0 kWh and takes 6.25 hours.
Key terms
- State of charge (SoC)
- The current charge level of the battery expressed as a percentage of its total capacity, analogous to a fuel gauge.
- Charger power (kW)
- The rate at which the charger delivers electrical energy to the battery, measured in kilowatts. Level 2 home chargers typically range from 3.3 to 19.2 kW.
- Energy needed (kWh)
- The amount of electrical energy that must be added to bring the battery from its starting charge to the target charge level.
- Charge time
- The estimated duration of the charging session, assuming the charger delivers its full rated power continuously.
- Charge tapering
- The automatic reduction in charging speed that occurs at high states of charge, especially on DC fast chargers, to protect battery cells. Not modelled by this simple estimate.
Frequently asked questions
- How long does it take to charge an EV?
- It depends on battery size and charger speed. A Level 2 7.2 kW charger adds about 25–30 miles per hour. A 50 kW DC fast charger can charge from 20–80% in about 30–60 minutes for a 75 kWh pack.
- Should I charge my EV to 100%?
- Most EV manufacturers recommend daily charging to 80% to preserve battery longevity. Only charge to 100% before a long trip when you need maximum range.