Start with energy you can actually use
Choose the real-world range calculator for a trip with a starting charge and an arrival reserve. It combines usable battery capacity with your consumption figure. A new-car capacity reference is useful context, but a current capacity measurement or estimate may be more relevant for a used vehicle.
Use recent consumption from driving that resembles your planned journey. Check the units before entering a figure. Kilometres per charge, kWh per 100 km and miles per kWh describe different things; the unit selector helps you enter them consistently.
Build a demanding scenario as well as a typical one
The winter calculator compares a normal-weather baseline with a range-loss band that you choose. It does not turn a temperature reading into an exact forecast. Heating use, speed and road conditions help describe the scenario so that you can compare similar trips.
Keep a reserve for detours and a charging stop that may be unavailable. If your consumption already reflects cold weather or motorway speeds, avoid adding the same effect twice. A lower range display alone does not prove permanent battery degradation. Use the battery evidence guides when the question is condition rather than trip planning.