Battery Energy Calculator
Formula Used
mAh to Wh: Wh = (mAh × Voltage) ÷ 1000.
Wh to mAh: mAh = (Wh × 1000) ÷ Voltage.
Ah to Wh: Wh = Ah × Voltage.
Wh to Ah: Ah = Wh ÷ Voltage.
How to Use This Calculator
- Select the required conversion direction.
- Enter battery capacity, energy, and voltage.
- Adjust pack, efficiency, runtime, and charging settings.
- Enter target runtime details when planning capacity.
- Select decimal precision and press Calculate.
- Copy, print, or export the final results.
Understanding mAh and Wh
Milliamp-hours measure electric charge stored by a battery. Watt-hours measure the battery's total stored energy. Voltage connects these two battery ratings.
Equal mAh ratings can store different energy amounts. A higher-voltage battery stores more watt-hours. Always compare batteries using matching voltage assumptions.
Series and Parallel Battery Packs
Series connections add individual cell voltages together. The pack capacity remains equal to one parallel group. This configuration is written using the letter S.
Parallel connections add cell capacities together. The pack voltage remains equal to one series string. This configuration is written using the letter P.
Worked Examples
| Example | Calculation | Result |
|---|---|---|
| 5,000 mAh at 3.7 V | (5,000 × 3.7) ÷ 1,000 | 18.5 Wh |
| 20,000 mAh at 5 V | (20,000 × 5) ÷ 1,000 | 100 Wh |
| 10 Ah at 12 V | 10 × 12 | 120 Wh |
| 100 Wh at 3.7 V | (100 × 1,000) ÷ 3.7 | 27,027.03 mAh |
Common Battery Voltages
| Battery type | Typical nominal voltage | Common use |
|---|---|---|
| NiMH cell | 1.2 V | Rechargeable household batteries |
| Alkaline cell | 1.5 V | Household electronics |
| LiFePO4 cell | 3.2 V | Energy storage systems |
| Lithium-ion cell | 3.6 V or 3.7 V | Phones, laptops, and tools |
| Lead-acid battery | 12 V | Vehicles and backup power |
Frequently Asked Questions
How do I convert mAh to Wh?
Multiply milliamp-hours by voltage, then divide by one thousand.
Why is voltage required?
Milliamp-hours measure charge, while watt-hours measure energy. Voltage links charge to usable energy.
Is 10,000 mAh always the same number of Wh?
No. The watt-hour value changes when the battery voltage changes.
How many Wh are in a 20,000 mAh power bank?
At 3.7 volts, it stores about 74 Wh. At 5 volts, the mathematical result is 100 Wh.
What is the difference between Ah and Wh?
Amp-hours measure charge capacity. Watt-hours include voltage and measure energy.
Does series connection increase Wh?
Yes. Series increases voltage, which increases total pack energy.
Does parallel connection increase Wh?
Yes. Parallel increases capacity, which also increases total pack energy.
How do efficiency losses affect usable energy?
Every loss reduces energy available to the connected device.
How can I estimate battery runtime?
Divide usable watt-hours by the device's average wattage.
Which voltage should I use?
Use the battery's nominal voltage unless a specification requires another value.
Can I convert Wh to mAh?
Yes. Multiply watt-hours by one thousand, then divide by voltage.