Use this EV battery degradation calculator to project an EV’s remaining battery capacity, driving range, and state of health over future years or miles.
EV Battery Degradation Formula
This calculator projects how much usable battery capacity an electric vehicle will keep in the future by applying a compounding degradation rate to the original capacity. The core formula is:
Cap(t) = Cap0 * (1 - r)^t
The state of health is simply the projected capacity divided by the original capacity, expressed as a percentage:
SoH% = Cap(t) / Cap0 * 100
Variables:
- Cap(t) is the projected remaining capacity (or driving range) after t periods
- Cap0 is the original capacity or range when the battery was new
- r is the degradation rate expressed as a decimal fraction per period (for example a 2.3 percent annual rate is r = 0.023)
- t is the number of periods: the number of years in age mode, or miles divided by 10,000 in mileage mode
- SoH% is the state of health, the share of original capacity still available
Note the difference between linear and compounding loss. A simple linear model subtracts the same amount every year, so after t years it removes r * t of the original capacity. The compounding model above applies the loss to the shrinking remaining capacity each period, so the pack never mathematically reaches zero and the yearly drop in kWh gets a little smaller over time. Compounding is the closer fit for how batteries actually fade, though real degradation is non-linear and typically steepest in the first year or two before it flattens out.
Enter the original figure either as capacity in kWh or as driving range in miles or kilometers, choose age or mileage mode, and the calculator returns the remaining capacity or range, the state of health percentage, and the amount lost at your chosen horizon.
Projected Capacity Retention by Year
This table shows the estimated state of health at a steady 2.3 percent annual degradation rate, a common real-world average. The right column applies that retention to a 75 kWh pack as a worked example.
| Age (years) | Remaining capacity (%) | 75 kWh pack |
|---|---|---|
| 1 | 97.7% | 73.3 kWh |
| 2 | 95.5% | 71.6 kWh |
| 3 | 93.3% | 69.9 kWh |
| 5 | 89.0% | 66.8 kWh |
| 8 | 83.0% | 62.3 kWh |
| 10 | 79.2% | 59.4 kWh |
| 12 | 75.6% | 56.7 kWh |
| 15 | 70.5% | 52.9 kWh |
At 2.3 percent per year the pack crosses the 70 percent mark, a common warranty threshold, at roughly 15 years. Cars driven in hot climates or fast charged often, or those with less durable chemistries, can reach that point sooner.
Example Problems
Example 1: Project remaining capacity by age.
A new EV has a 75 kWh battery and you assume 2.3 percent degradation per year. To see where it stands after 8 years, raise the retention factor to the eighth power:
Cap(8) = 75 * (1 – 0.023)^8 = 75 * 0.8302 = 62.3 kWh. That is a state of health of about 83 percent, meaning roughly 12.7 kWh has been lost.
Example 2: Project remaining range by mileage.
A crossover EV was rated at 250 miles of range when new and loses about 1.0 percent per 10,000 miles. After 60,000 miles the exponent is 60,000 / 10,000 = 6:
Range = 250 * (1 – 0.01)^6 = 250 * 0.9415 = 235.4 miles, a state of health near 94.1 percent, with about 14.6 miles of range lost.
Frequently Asked Questions
How much do EV batteries degrade per year?
Large fleet studies put the average at roughly 1 to 2.3 percent of capacity per year, with recent data trending toward the lower end near 1.8 percent as battery management and chemistry improve. Real degradation is fastest in the first year or two, then settles into a slow, steady decline, so a single yearly figure is an average rather than a fixed step.
How long until an EV battery hits 70%?
At a steady 2.3 percent compounding annual rate it takes about 15 years to fall to 70 percent of the original capacity. Most manufacturers warranty the battery to stay above about 70 percent for 8 years or 100,000 miles, so hitting that floor within the warranty window is uncommon for a typical car. Heavy fast charging and hot climates can shorten the timeline.
What speeds up battery degradation?
Heat is the biggest factor, so hot climates and parking or charging in high temperatures accelerate loss. Frequent DC fast charging, regularly charging to 100 percent, deep discharges to near empty, and very high annual mileage all add stress. Keeping the state of charge roughly between 20 and 80 percent for daily use, and limiting fast charging to when it is needed, helps the pack last longer.
