mAh to kWh Calculator
This calculator converts battery capacity from milliamp-hours (mAh) into kilowatt-hours (kWh), using the voltage. It's useful for understanding how much large-scale energy small batteries store.
Why Convert mAh to kWh?
Milliamp-hours (mAh) are commonly used to describe the capacity of small batteries—such as those in phones, wearables, or portable gadgets. Kilowatt-hours (kWh), on the other hand, are a much larger unit used to describe total energy consumption or generation—such as household electricity bills or solar panel outputs. Converting mAh to kWh helps bridge the gap between small-scale battery capacities and large-scale energy calculations.
Whether you're comparing phone batteries to household energy use, or evaluating how much energy a battery bank will require to recharge a fleet of devices, this conversion is extremely helpful.
Conversion Formula: mAh to kWh
To convert from mAh to kWh, you need to include the battery voltage, since energy (in Wh or kWh) depends on both charge (Ah/mAh) and voltage (V).
kWh = (mAh × V) / 1,000,000
- mAh: battery capacity in milliamp-hours
- V: battery voltage (typically 3.6–3.7V for lithium-ion)
- 1,000,000: converts from milliwatt-hours (mWh) to kilowatt-hours (kWh)
Example:
A 5000mAh phone battery at 3.7V:
5000 × 3.7 = 18,500 mWh = 0.0185 kWh
Use Cases for This Conversion
- Energy audits: Understand how much energy thousands of mAh-based devices consume cumulatively.
- Power backup design: Calculate how many phones, flashlights, or other mAh-powered devices can be supported by a UPS, solar battery, or generator.
- Product comparison: Convert marketing specs from mAh to kWh for better understanding of actual energy content.
- Power bank design: Reverse-engineer the energy stored in a portable charger and how it affects recharge cycles.
Real-World Examples
- Example 1: Phone battery
A 4000mAh battery at 3.7V:
4000 × 3.7 / 1,000,000 = 0.0148 kWh
That’s roughly 1.48% of a kilowatt-hour. - Example 2: USB power bank
A 20,000mAh battery at 3.7V:
20,000 × 3.7 = 74,000 mWh = 0.074 kWh - Example 3: Bulk device energy usage
Charging 1,000 smartphones, each with a 3000mAh battery @ 3.7V:
3000 × 3.7 = 11,100 mWh × 1000 = 11.1 kWh
This would cost roughly $1.66 at $0.15/kWh electricity rate.
Common Voltage Values for mAh-Based Devices
| Device | Typical Voltage |
|---|---|
| Smartphone battery | 3.6–3.85 V |
| Portable power bank | 3.7 V (internal cells) |
| Tablet | 3.7–7.4 V |
| USB fan/light | 3.0–5.0 V |
| Wearables (smartwatch, tracker) | 3.7 V |
How Much Is 1 kWh in mAh?
To understand scale, we can reverse the calculation:
At 3.7V: 1 kWh = 1,000,000 mWh / 3.7 = ~270,270 mAh
So, it takes more than 270,000mAh at 3.7V to store 1 kWh of energy. That’s like charging 54 phones with 5000mAh batteries.
Accounting for Efficiency
Real systems aren't perfectly efficient. Energy losses occur during:
- Charging (heat and internal resistance)
- DC to DC boost or buck conversions
- Battery aging and degradation
For practical calculations, apply an efficiency factor:
Usable kWh = Theoretical kWh × Efficiency (e.g., 0.9)
Frequently Asked Questions (FAQ)
Can I use this conversion for all battery types?
Yes, the math applies universally, but voltage must match the battery chemistry. Lithium-ion batteries use 3.6–3.7V; NiMH around 1.2V; lead-acid uses 2V per cell (12V system = 6 cells).
Is mAh the same as battery life?
No. mAh tells you charge capacity, not time. Battery life depends on how fast energy is consumed (power draw in watts).
How much does it cost to charge a 10,000mAh phone?
At 3.7V: 10,000 × 3.7 = 37,000 mWh = 0.037 kWh.
At $0.15/kWh, that’s 0.037 × 0.15 = ~$0.0055 (half a cent).
Can I convert Wh to mAh first and then to kWh?
You can, but it's unnecessary. It’s more direct to go:
kWh = (mAh × V) / 1,000,000
The intermediate Wh step is:
mAh × V = mWh → divide by 1000 = Wh → divide by 1000 again = kWh
How do I compare power banks with different voltages?
Convert mAh to Wh first: (mAh × V) / 1000 = Wh. Then compare energy capacity directly. Wh or kWh gives a more accurate energy comparison than mAh alone.
Conclusion
Converting milliamp-hours (mAh) to kilowatt-hours (kWh) is essential when scaling small battery data to larger systems or cost/usage estimates. Whether you're an engineer, solar system planner, or just curious how many phone charges a generator can provide, this tool gives a fast, practical translation. Always factor in voltage, system efficiency, and real-world behavior to get the most from your calculations.