EV Battery Degradation Calculator

This calculator estimates that change from the battery's original usable size, its original driving range, an expected annual degradation rate, and years of use. It reports retained capacity, lost capacity, remaining kilowatt-hours, and proportional range. The calculation is deterministic and useful for comparisons, budgeting, and long-term planning, but it does not replace a vehicle-specific battery health test.

Enter comparable starting values

Start with the vehicle's original usable battery capacity, not necessarily the larger gross capacity advertised for the physical pack. Manufacturers may reserve energy buffers that drivers cannot access, so gross and usable figures can differ. Then enter an original range measured under a consistent basis. An official test-cycle rating is suitable when you want to estimate how that same rating might change, while a personal warm-weather baseline is better for comparing your own driving. Avoid mixing an official laboratory range with a recent winter observation, because temperature, cabin heating, speed, wind, elevation, tire pressure, and driving style can move range independently of degradation. The annual degradation rate is expressed as a percentage of the capacity remaining at the beginning of each year. Years may include a fractional part, which is helpful for a vehicle that is, for example, four and a half years old. Keeping the starting capacity and range on comparable terms makes the output easier to interpret and avoids attributing ordinary efficiency differences to battery aging.

Understand the compounded calculation

The calculator uses geometric compounding. For an annual degradation rate r and an age y, the retained fraction is calculated as (1 - r) raised to the power y. Remaining battery capacity equals the original usable capacity multiplied by that retained fraction. Estimated range is calculated by multiplying the original range by the same fraction. This means a two percent annual rate does not simply remove twenty percent over ten years: each year's loss is applied to a slightly smaller remaining capacity. The output includes both retention and loss percentages, remaining and lost kilowatt-hours, and estimated remaining and lost range. Results are rounded to six decimal places for stable reporting, although the precision of the estimate is limited by the assumptions you enter. A constant annual rate is a simplified planning model. Real packs may degrade faster early in life, settle into a slower period, and change again with age, mileage, charging habits, thermal exposure, chemistry, or individual cell condition.

Use the result as a scenario, not a diagnosis

Treat the estimate as a controlled scenario for answering questions such as whether an older vehicle could still cover a commute or how much usable energy might remain near the end of an ownership period. It is especially useful for comparing several degradation assumptions: run a conservative rate, a middle estimate, and an optimistic rate while holding the starting values constant. The resulting range assumes energy consumption per kilometer stays unchanged. In real driving, efficiency can vary enough to outweigh modest battery degradation, so a lower observed range alone does not prove that the battery has lost the same percentage of capacity. For a vehicle-specific assessment, consult its battery management system data, a qualified diagnostic report, or a repeatable full-charge energy test. Also check how the manufacturer defines state of health and warranty thresholds, because those definitions may not match this simple usable-capacity model. The API price is $0.002 per request, and the same deterministic calculation can support repeatable planning tools and ownership comparisons.