myevnumbers
Calculator / Miles Needed
Journey planner

Miles Needed

Work backwards from a journey to the charge percentage, energy, cost and time required.

The journey distance you need the newly added charge to cover. Include the return trip where relevant.
Extra miles to leave as a buffer for weather, diversions or unavailable chargers. This is added to Miles needed.
The vehicle’s usable battery capacity in kWh, not its advertised gross capacity.
The battery percentage shown by the car before charging.
The maximum power the charger can supply in kW.
The maximum power the vehicle can accept from this type of charger. The lower of this and Charger power limits the speed.
The electricity price for this charging session in pence per kWh. Enter 24 for 24p/kWh.
Electricity used but not stored in the battery. Leave at 10% if unsure.
Expected driving efficiency in miles per kWh. Use a cautious figure for winter or motorway journeys.

How much battery charge do you need for a journey?

The calculator converts journey distance into battery energy using your expected miles per kWh, then adds your chosen arrival reserve. It compares that target with the battery’s starting percentage to estimate the top-up required.

Choose a realistic efficiency

Use a recent average that matches the trip. Motorway speeds, cold weather, rain, hills and cabin heating can reduce efficiency, so a cautious figure is sensible for an unfamiliar route.

Keep an arrival reserve

A reserve allows for diversions, a busy or unavailable charger and normal variation in range. The right margin depends on the route and your comfort level.

Compare temperature and motorway estimates with the UK real-world EV range calculator.