The battery capacity calculator is an excellent choice if you want to know what battery capacity is or if you need to compute the properties of various batteries and compare them before purchasing a new battery.
We need batteries to power our phones, laptops, and cars, and knowing how to calculate their amp hours is a crucial thing. In the following text, you can read more about this battery charge calculator, learn about the battery capacity formula, and see how you can use this tool as a 12 V battery run time calculator in an example. Stay tuned!
What is battery capacity?
The capacity of a battery is the amount of energy that it can store. A battery's capacity is expressed in amp hours (Ah), which is a measure of electrical current over time. One amp hour equals one amp of current flowing for one hour. The higher the Ah, the longer the battery will last.
We show the battery Ah calculation below, together with a battery amp hours chart at the very end of this article.
We also have an interesting text and calculator about different types of horsepower units, including electrical horsepower. Check the hp to amps calculator to learn more!
How to calculate amp hours
To calculate amp hours, you need to know the voltage of the battery and the amount of energy stored in the battery. Multiply the energy in watt-hours by voltage in volts, and you will obtain amp hours.
Alternatively, if you have the capacity in mAh and you want to make a battery Ah calculation, simply use the equation:
Ah = (capacity in mAh)/1000. For example, if a battery has a capacity of
3000 mAh, then its Ah rating would be
Finally, to calculate the capacity of a battery in amp hours, you can use the current flowing in the battery and the amount of time that the battery can provide power at that current and multiply both values:
amp hours = current × time. For example, if you have a 12-volt battery that can provide 1 amp of current for 3 hours, the capacity of the battery is:
amp hours = 1 amps × 3 hours = 3 amp hours.
Battery capacity formula
We have already shown various methods explaining how to calculate amp hours (
Ah). Let's now see the particular battery capacity formulae:
Ah = watt-hours × voltage
Ah = mAh / 1000
Ah = discharge current × time (hours)
Our battery calculator offers a quick estimation of all the above equations depending on your needs. To use the second equation, enter the battery capacity in Ah, and then switch the units to mAh.
How to use the battery capacity calculator
The tool on this website can work in various ways:
- Battery capacity calculator - enter voltage and watt-hours, and you will obtain battery capacity in ampere-hours.
- Battery charge calculator (or battery kWh calculator) - enter voltage and ampere-hours to find watt-hours and, thus, the battery charge.
- Battery charge time calculator - input C-rate (one C-rate is equal to a battery working for 1 hour with 100 amperes) or battery capacity and discharge current to find how long you need to wait to fully charge or discharge the battery.
Battery amp hours chart
If you prefer a chart over a battery calculator, we have prepared two charts that you can use instead. The first one tells you what capacity your battery has depending on the voltage and watt-hours, while the second one estimates how long your battery will run with a specific capacity and discharge current.
16 hrs 40 min
33 hrs 20 min
66 hrs 40 min
166 hrs 40 min