Enter the total voltage and the watt-hours of a battery into the calculator to determine the battery capacity, also known as amp-hours.

Battery Capacity Formula

The following formula us used to calculate a battery capacity in amp-hours:

 E = V * Q 
  • Where E is the energy stored in the batter in watt-hours
  • V is the voltage of the battery
  • and Q is the capacity

Re-arranging this equation and we find that,

Q = E/V

Which is the formula used by the calculator above to determine amp hours.

Battery Capacity Definition

A battery capacity is defined as the total energy storage that a battery can hold.

How to calculate the amp hour capacity of a batter

The following example is a step-by-step guide on how to calculate the capacity of a battery in amp-hours.

  1. The first step to solving this problem is to analyze the equation E = V * Q to see which variables we need to solve for capacity. Since Q is capacity in amp-hours, then we need to find both the energy store E and the voltage, V.
  2. The next step is to determine the total energy stored in the battery. This unit is usually measured in watt-hours and is often provided as published data by the battery maker. (or car if you are talking electric cars.) For this example, we will assume this value to be 1000 watt-hours.
  3. Next, you must determine the total voltage of the energy stored or emitted from the batter. This is also typically published data, and most often is around 120 Volts, so we will use that value as an example in this problem
  4. The final step is to plug this information into the formula above, so Q = E/V = 1000/120 = 8.333 amp-hours.
  5. Analyze the results and apply learning to future problems.


What is a battery capacity?

A battery capacity is defined as the total energy storage that a battery can hold.