Car & Vehicle

EV Charging Time Calculator

How long an EV charge takes, with the slowdown above 80% allowed for on fast charging and left out where it does not apply.

6 inputs Free, no sign-up

Your figures

From the handbook or the manufacturer's specification. Usable capacity is a little below the gross figure, because a buffer is held back at each end to protect the cells - and it differs by variant, so it is not filled in here.

What the car actually accepts, not the charger's headline rating. A 50 kW charger cannot push 50 kW into a car whose onboard limit is 7.

A fast charger backs off above 80%; a slow one never reaches the limit that causes it, so the taper is applied to one and not the other.

Leave blank to use this page's assumption, which the result names. Charging is not lossless - some of what the meter counts becomes heat in the charger, the cable and the battery.

Try an example

Result

Your result

Enter your figures and the result appears here.

Estimates only. Rates, fees and specifications change. Confirm against the official source before you rely on a figure — see our disclaimer.

About this calculator

Dividing the energy by the charger's rating gives an answer that is roughly right up to 80% and badly optimistic past it — on a fast charger. A battery accepts a high rate only while there is room; as it fills, the charger backs off, so the last fifth can take as long as the first four.

On a home socket none of that applies, because 3 kW is nowhere near what the battery would accept. This page asks which kind of charging you mean and applies the taper only where it belongs.

How to use this calculator

  1. Enter the usable battery capacity.
  2. Set the starting and target charge.
  3. Enter the charging power in kW — what the car accepts, not the charger's headline number. A 50 kW charger cannot push 50 kW into a car limited to 7.
  4. Say whether this is DC fast charging or AC charging at home.

The formula

Energy to add  = Capacity x (Target - Start) / 100
Below 80%      = that share of the energy / (Power x Efficiency)
Above 80%      = that share x 2 / (Power x Efficiency)   [DC only]
Time           = the two added together

The factor of two above 80% is a convention, not a measurement, and the result says so. It is conservative and it varies by car; charging to 80% instead avoids the question entirely, which is why public charging sessions are usually quoted to 80%.

SymbolMeaningUnit
Capacity Usable battery capacity kWh
Power What the car accepts kW
Efficiency Share reaching the battery %

Worked example

A 40 kWh battery from 10% to 100% on a 50 kW charger, 85% efficiency:

Energy to add = 40 x 0.90        = 36 kWh
10% to 80%    = 28 / (50 x 0.85) = 0.66 hours
80% to 100%   = 8 x 2 / 42.5     = 0.38 hours
Total                             = 1.04 hours

Stopping at 80% would have taken 40 minutes for 28 of those 36 kWh.

Notes and limits

  • The rate a session actually runs at is the lowest of the charger, the cable, the car's onboard limit and what the battery will accept at its current temperature and state of charge. The headline number on the charger is only one of those four.
  • Cold batteries charge slowly. A car that has not been preconditioned can take far longer than this on a fast charger in winter.
  • AC charging is limited by the car's onboard charger, which is commonly 3.3, 7.2 or 11 kW regardless of what the wall box could supply.
  • A 15 A household socket delivers roughly 2.5 to 3 kW. That is an overnight charge, not an hour's one.
  • The EV charging cost calculator answers the other half.

What this calculation assumes

  • The taper above 80% is modelled at roughly twice the time per kWh, on DC charging only. It is an assumption and varies by vehicle.
  • Charging power is taken as constant below 80%, which cold weather and a hot battery both break.
  • Battery capacity and charging power are figures you entered.

Frequently asked questions

How long does it take to charge an electric car?

Divide the energy you are adding by the power the car accepts, then allow for losses. A 40 kWh battery from 10% to 80% at 50 kW takes about 40 minutes; the same battery on a 3 kW home socket takes around eleven hours.

Why does charging slow down above 80%?

A lithium battery takes a high current only while there is room for the charge. As it fills, the charger holds the voltage and lets the current fall away to protect the cells. On a fast charger that is very noticeable; on a slow one the rate was never high enough for it to matter.

Should I enter the charger's rating or the car's?

Whichever is lower - that is what the session will run at. A 50 kW charger and a car limited to 25 kW gives a 25 kW session.

Is it worth charging to 100% on a fast charger?

Usually not. The last 20% can take as long as the first 70 and costs the same per unit, so on a long trip two stops to 80% are normally quicker than one to 100%.

Related calculators