## CALCULATE YOUR BATTERY LIFE OF YOUR DRONE

If you want to convert between amp hours and watt-hours or find the C-rate of a battery, give this battery capacity calculator a try. It is a handy tool that helps you understand how much energy is stored in the battery that your smartphone or a drone runs on. Additionally, it provides you with a step-by-step instruction on how to calculate amp hours and watt-hours, so you will be able to perform all of these calculations by yourself, too!

Wondering how long your electrical device will run on this battery? Check out the battery life calculator!

## What are battery amp hours?

The primary function of a battery is to store energy. We usually measure this energy in watt-hours, which correspond to one watt of power sustained for one hour.

If we want to calculate how much energy – so, in other words, how many watt-hours – are stored in a battery, you need information about the electric charge in the battery. This value is commonly expressed in **amp hours** – amps (units of electric current) multiplied by hours (units of time).

## Battery capacity formula

As you might remember from our article on Ohm’s law, the power **P** of an electrical device is equal to voltage **V** multiplied by current **I**:

`P = V * I`

As energy **E** is power **P** multiplied by time **T**, all we have to do to find the energy stored in a battery is to multiply both sides of the equation by time:

`E = V * I * T`

Hopefully, you remember that amp hours are a measure of electric charge **Q** (the battery capacity). Hence, the final version of the **battery capacity formula** looks like this:

`E = V * Q`

where

**E**is the energy stored in a battery, expressed in watt-hours;**V**is the voltage of the battery;**Q**is the battery capacity, measured in amp hours.

## How to calculate amp hours?

Let’s assume you want to find out the capacity of your battery, knowing its voltage and the energy stored in it.

- Note down the voltage. In this example, we will take a standard 12V battery.
- Choose the amount of energy stored in the battery. Let’s say it’s 26.4 Wh.
- Input these numbers into their respective fields of the battery amp hour calculator. It uses the formula mentioned above:

`E = V * Q`

`Q = E / V = 26.4 / 12 = 2.2 Ah`

- The battery capacity is equal to 2.2 Ah.

## Battery capacity calculator: advanced mode

If you open the advanced mode of this battery capacity calculator, you will be able to compute three other parameters of a battery.

**C-rate of the battery.**C-rate is used to describe how fast a battery charges and discharges. For example, a 1C battery needs one hour at 100 A to load 100 Ah. A 2C battery would need just half an hour to load 100 Ah, while a 0.5C battery requires two hours.**Discharge current.**This is the current**I**used for either charging or discharging your battery. It is linked to the C-rate with the following equation:`I = C-rate * Q`

**Runtime to full capacity.**It is simply the time**t**needed to fully charge or discharge the battery when using the discharge current, measured in minutes. You can calculate it as`t = 1/C`

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**Bogna Haponiuk**