Battery energy to range reverse estimator
A reverse-style question: given the battery energy you have left, how far can you actually go? Useful for planning whether you need to charge before a journey.
Result
Estimated range
How to use this tool
- Check your car's remaining battery energy (some cars show this directly; otherwise multiply battery capacity by remaining %).
- Enter your efficiency in miles per kWh (use your trip computer's real-world average).
- Read the estimated range.
Assumptions
- Assumes constant efficiency for the whole remaining journey — motorway speed, cold weather, hills and load all reduce real efficiency.
- Does not reserve a safety buffer — treat the result as a maximum, not a target.
Technical details: what the fields mean
- Available battery energy
availableEnergyKwh - Usable energy remaining in the battery, in kWh.
- Efficiency
efficiencyMiPerKwh - Your car's real-world efficiency, in miles per kWh.
Methodology
Range = available energy × efficiency. This is the inverse of the usual "miles + efficiency → energy required" question.
Worked example
18kWh remaining, 3.5 mi/kWh efficiency
Inputs: Available battery energy: 18 kWh, Efficiency: 3.5 mi/kWh
Result: 63 miles estimated range
Practical guidance
- Build in a safety margin — don't plan a journey to exactly this figure, especially in cold weather or at motorway speeds where efficiency drops.
- Use your car's own real-world efficiency rather than the manufacturer's official figure for a realistic estimate.
Common mistakes
- Using summer/mild-weather efficiency to estimate winter range, which is typically noticeably lower.
FAQs
How far can I go on 18kWh of remaining battery?
At 3.5 mi/kWh, roughly 63 miles — build in a safety margin rather than planning to this exact figure.
Last reviewed: 2026-09-24
Real-world range varies with speed, weather, terrain and load — treat this as an estimate, not a guarantee.
This tool provides an indicative estimate, based on the assumptions stated above.
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