mAh to kWh Calculator
Convert battery capacity in mAh to kWh, and estimate charging energy and cost.
Formula: kWh = (mAh × V) / 1,000,000
What this mAh kWh calculator does
This tool converts battery capacity from milliamp-hours (mAh) into kilowatt-hours (kWh), which is the energy unit used on utility bills and most large energy systems. If you are comparing a power bank to a solar battery, estimating charging costs, or planning backup power, this conversion gives you a practical apples-to-apples number.
In short: mAh alone is not enough. You must include voltage to calculate real energy.
mAh vs Wh vs kWh: quick definitions
- mAh (milliamp-hours): charge capacity. Common on phones, power banks, and lithium cells.
- Wh (watt-hours): energy capacity. Better for comparing batteries across voltages.
- kWh (kilowatt-hours): 1,000 Wh. Used for home batteries and electricity costs.
Because two batteries can have the same mAh but different voltage, they can store different actual energy.
The conversion formula
mAh to Wh
mAh to kWh
Reverse (kWh to mAh)
Worked examples
Example 1: Phone battery
A 5,000 mAh battery at 3.85 V stores:
- Wh = (5000 × 3.85)/1000 = 19.25 Wh
- kWh = 19.25/1000 = 0.01925 kWh
Example 2: 20,000 mAh power bank
For a 20,000 mAh power bank rated at 3.7 V:
- Wh = 74 Wh
- kWh = 0.074 kWh
If electricity is $0.16/kWh and charging efficiency is 85%, wall energy is approximately 0.087 kWh, and a full charge costs about $0.014.
Example 3: Battery pack with multiple cells
If each battery is 10,000 mAh at 12 V and you have 4 of them:
- Per battery: 0.12 kWh
- Total stored: 0.48 kWh
Quick reference table
| Capacity (mAh) | Voltage (V) | Energy (Wh) | Energy (kWh) |
|---|---|---|---|
| 3,000 | 3.7 | 11.1 | 0.0111 |
| 5,000 | 3.85 | 19.25 | 0.01925 |
| 10,000 | 3.7 | 37 | 0.037 |
| 20,000 | 3.7 | 74 | 0.074 |
| 50,000 | 12 | 600 | 0.6 |
Common mistakes to avoid
- Ignoring voltage: mAh without voltage cannot tell you true energy.
- Assuming 100% efficiency: real charging and inverter losses matter.
- Mixing nominal and max voltage: use nominal battery voltage for realistic comparisons.
- Comparing only marketing numbers: always convert to Wh or kWh first.
When this calculator is useful
- Comparing power banks and battery packs
- Sizing off-grid or emergency backup systems
- Estimating how much a full battery charge costs
- Converting electronics battery specs into utility-bill units
FAQ
Is higher mAh always better?
Not always. Higher mAh usually means more stored charge, but total energy also depends on voltage. A lower mAh battery at higher voltage can store more energy than a higher mAh battery at lower voltage.
Why does my charging cost estimate seem tiny?
Small batteries store a relatively small amount of energy. Even at high electricity rates, a single phone charge is often only a few cents or less.
Can I use this for lithium-ion, LiFePO4, and lead-acid batteries?
Yes. The conversion math is universal. Just enter the proper nominal voltage and capacity for your chemistry and pack configuration.
Use the calculator above whenever you need a fast, accurate battery capacity conversion from mAh to kWh, plus a practical estimate of real charging energy and cost.