Quick Answer: To convert mWh to mAh, divide by voltage (mAh = mWh ÷ V). To convert mAh to mWh, multiply by voltage (mWh = mAh × V).
Use our calculator below for instant conversions with voltage presets for common battery types.
⚡ Quick Reference
Formula: mAh = mWh ÷ Voltage
Example: 7,400 mWh ÷ 3.7V = 2,000 mAh
Common Use: Convert battery specs from energy (mWh) to charge (mAh)
Need to Convert mAh to mWh?
mWh vs mAh: What's the Difference?
Understanding the difference between mWh (milliwatt-hours) and mAh (milliamp-hours) is crucial for comparing batteries and understanding device specifications.
| Aspect | mWh (Milliwatt-Hours) | mAh (Milliamp-Hours) |
|---|---|---|
| What It Measures | Energy capacity | Charge capacity |
| Formula | mWh = mAh × Voltage | mAh = mWh ÷ Voltage |
| Depends On | Both charge AND voltage | Charge only (voltage-independent) |
| Better For Comparison | ✓ Yes - compares actual energy | Only if voltages are the same |
| Common Usage | Technical specs, energy ratings | Consumer marketing, battery labels |
| Example | 7,400 mWh (actual energy) | 2,000 mAh @ 3.7V (needs voltage) |
Key Takeaway
mWh tells you how much work the battery can do. Two batteries with the same mAh rating but different voltages have different energy capacities. Always convert to mWh (or Wh) when comparing batteries with different voltages.
Real Example:
- Battery A: 2,000 mAh @ 3.7V = 7,400 mWh
- Battery B: 2,000 mAh @ 5V = 10,000 mWh
- Result: Battery B has 35% more energy despite identical mAh ratings!
Conversion Formulas
mAh = mWh ÷ V
mWh = mAh × V
Where V is the voltage in volts
📱 Real-World Device Examples
See how these calculations apply to devices you use every day:
Battery: 523 mWh @ 3.7V = 141 mAh
Listening time: ~6 hours per charge
Battery: 1,280 mWh @ 3.85V = 332 mAh
Battery life: Up to 18 hours of typical use
Battery: 180 mWh @ 3.8V = 47 mAh
Battery life: Up to 7 days per charge
Battery: 61 mAh @ 3.85V = 235 mWh
Playback time: 5 hours (8 hours with ANC off)
Battery: 10,000 mAh @ 3.7V = 37,000 mWh (37 Wh)
Can charge iPhone 13 approximately 2.5 times
Battery: 340 mWh @ 3.8V = 89 mAh
GPS mode: 30 hours, Smartwatch mode: 14 days
⚡ Common Battery Voltages Reference
| Battery Type | Nominal Voltage | Full Charge | Common Uses |
|---|---|---|---|
| AA/AAA Alkaline | 1.5V | 1.65V | Remote controls, toys, flashlights |
| AA/AAA NiMH Rechargeable | 1.2V | 1.4V | Cameras, gaming controllers |
| Lithium-ion (Li-ion) Single Cell | 3.7V | 4.2V | Smartphones, tablets, laptops |
| Lithium-polymer (LiPo) | 3.7V | 4.2V | Drones, RC vehicles, wearables |
| LiFePO4 (Lithium Iron Phosphate) | 3.2V | 3.65V | Solar systems, electric vehicles |
| USB Standard Output | 5V | 5V | Power banks, USB charging devices |
| Car/Automotive (Lead-Acid) | 12V | 12.6V | Vehicles, portable fridges, RVs |
| Small Solar Systems | 24V | ~28V | Off-grid solar, RV systems |
| Large Solar Systems | 48V | ~56V | Home energy storage, commercial |
Example Calculations
| Given | Voltage | Result |
|---|---|---|
| 7,400 mWh | 3.7V | 2,000 mAh |
| 3,700 mWh | 3.7V | 1,000 mAh |
| 1,500 mWh | 1.5V | 1,000 mAh |
| 2,000 mAh | 3.7V | 7,400 mWh |
| 5,000 mAh | 5V | 25,000 mWh (25 Wh) |
Understanding the Relationship
Energy (mWh) = Charge (mAh) × Voltage (V)
Think of it like a water system:
- mAh (charge) = Amount of water in the tank (volume)
- Voltage = Water pressure pushing through pipes
- mWh (energy) = Total work the water can do (volume × pressure)
A battery with higher voltage does more work with the same charge capacity. That's why you need voltage to convert between energy (mWh) and charge (mAh). They measure fundamentally different properties!
Why manufacturers use different units:
- mAh is common in consumer marketing because it's easier to understand and compare within the same voltage class
- mWh (or Wh) gives actual energy capacity, essential for comparing batteries with different voltages
- Technical specs often include both: mAh for charge capacity and Wh for energy capacity
Real-world example: A 10,000 mAh power bank at 3.7V nominal voltage contains 37 Wh of energy. But when it outputs at 5V USB, conversion losses mean you'll get about 6,500-7,000 mAh delivered to your 5V device.
Frequently Asked Questions (FAQs)
1. What is the difference between mWh and mAh?
mWh (milliwatt-hours) measures energy capacity - the total amount of work a battery can do. mAh (milliamp-hours) measures charge capacity - the amount of electrical charge stored. The relationship is: mWh = mAh × Voltage. Energy depends on both charge AND voltage, which is why you can't compare batteries by mAh alone if they have different voltages.
2. Can I convert mWh to mAh without voltage?
No. Voltage is required because energy and charge are related through voltage (Energy = Charge × Voltage). Without knowing the voltage, mAh cannot be determined accurately. If you see a battery rated only in mWh, you must find its voltage specification to calculate mAh.
3. How do you convert mWh to mAh?
Divide milliwatt-hours by voltage: mAh = mWh ÷ V. For example, a battery with 7,400 mWh at 3.7V equals 2,000 mAh (7,400 ÷ 3.7 = 2,000). Use our calculator above for instant results.
4. Where is mWh commonly used?
mWh ratings appear in technical battery specifications for smaller devices like wireless earbuds, fitness trackers, smartwatches, and other wearables. It's also used in energy regulations and battery labeling in some regions. Larger batteries typically use Wh (watt-hours) instead of mWh.
5. Is this calculation accurate for all battery types?
Yes, as long as the voltage is correctly provided. The formula works for all battery chemistries including lithium-ion, lithium-polymer, NiMH, alkaline, and lead-acid batteries. The physics of energy = charge × voltage is universal across all battery types using standard SI units.
6. How do I go from mAh to mWh?
Multiply milliamp-hours by voltage: mWh = mAh × V. For example, 2,000 mAh at 3.7V equals 7,400 mWh (2,000 × 3.7 = 7,400). The second calculator on this page handles this conversion automatically.
7. Why do power banks show mAh but energy is in Wh?
Power banks show mAh based on the internal battery cells (usually 3.7V nominal). However, they output at 5V USB, so the deliverable capacity is lower due to voltage conversion. The Wh (watt-hour) rating shows true energy capacity. A 10,000 mAh @ 3.7V power bank = 37 Wh, which delivers about 7,000 mAh at 5V after conversion losses.
8. What's the difference between nominal and actual battery capacity?
Nominal capacity is the rated capacity under ideal conditions (specific temperature, discharge rate). Actual capacity depends on discharge rate, temperature, battery age, and usage patterns. Real-world capacity is typically 85-95% of nominal rating. High discharge rates reduce capacity further.
9. Is 1000 mWh the same as 1 Wh?
Yes! 1,000 milliwatt-hours (mWh) equals 1 watt-hour (Wh). The "milli" prefix means one-thousandth, just like millimeters to meters. For larger batteries, Wh is more commonly used (e.g., laptop batteries are 50-100 Wh, not 50,000-100,000 mWh).
10. Can I use this for car batteries?
Yes, but car batteries are typically rated in amp-hours (Ah), not milliamp-hours. A typical car battery is 50-70 Ah @ 12V = 600-840 Wh. For mAh conversion: 50 Ah = 50,000 mAh. For mWh: 50,000 mAh × 12V = 600,000 mWh = 600 Wh.
11. How long will my battery last?
Battery life = (Battery capacity in mAh) ÷ (Device current draw in mA). For example, a 2,000 mAh battery powering a device drawing 100 mA will last approximately 20 hours (2,000 ÷ 100 = 20). Use our battery runtime calculator for more accurate estimates accounting for efficiency losses.
12. What voltage should I use for USB devices?
Standard USB outputs 5V. USB-A typically provides 5V at 0.5-2.4A. USB-C can provide 5V, 9V, 12V, 15V, or 20V depending on Power Delivery (PD) negotiation. For basic USB calculations, use 5V. Check your device specifications for USB-C fast charging voltages.
Common Applications
- Small electronics: Wireless earbuds, smartwatches, fitness trackers, medical devices
- Battery testing: Lab testing and quality control for battery manufacturers
- Solar-powered gadgets: Estimating charge intake and consumption rates for off-grid devices
- DIY electronics: Arduino projects, Raspberry Pi, IoT devices - selecting appropriate batteries
- Battery replacement: Finding equivalent capacity replacements when original specs use different units
- Power bank comparison: Comparing actual energy capacity across different brands and models
- Drone and RC vehicles: Calculating flight time and selecting appropriate battery packs
- Electric vehicle conversion: Planning battery pack energy requirements
💡 Pro Tips for Battery Selection and Comparison
When comparing batteries with different voltages, always convert to Wh (watt-hours) for accurate comparison. A 5,000 mAh @ 3.7V battery (18.5 Wh) has less energy than a 4,000 mAh @ 5V battery (20 Wh), despite the lower mAh rating!
For power banks, look for both mAh AND Wh ratings in the specifications. The Wh rating tells you actual usable energy after accounting for voltage conversion losses from the internal battery (3.7V) to USB output (5V).
Battery capacity decreases at high discharge rates. A battery rated for 2,000 mAh at 0.2C (400 mA) may only deliver 1,700 mAh at 1C (2,000 mA). Check the battery's C-rating and discharge curves for accurate performance specs.
DC-DC converters (voltage regulators) have efficiency losses, typically 10-20%. When converting voltage up or down, expect to lose this amount of energy. A 10,000 mAh @ 3.7V power bank (37 Wh) might only deliver 6,500-7,000 mAh at 5V due to these losses.
Battery capacity drops in cold temperatures. Li-ion batteries can lose 20-40% capacity at freezing temperatures. If using batteries in cold environments, size your battery bank 30-50% larger than calculated requirements.
Related Battery & Energy Calculators
Convert milliamp-hours to watt-hours for battery capacity 🔋 Battery Runtime Calculator
Calculate how long your batteries will last under load ⚡ Amps to Milliamps
Convert between amps and milliamps for current calculations ☀️ Solar Charge Controller
Size your solar charge controller properly 🔌 Wire Sizing Calculator
Determine correct wire gauge for your current and voltage 🧮 Solar System Calculator
Design your complete off-grid solar power system
Ready to Calculate Your Solar Savings?
Now that you've determined your battery capacity, it's time to see how much money you could save by going solar in your province.
Electricity rates vary dramatically across Canada—from Quebec's 7.8¢/kWh to Northwest Territories' 41¢/kWh. Your location directly impacts:
- Solar system payback period (8-25 years depending on province)
- Annual savings potential ($500-$3,000+ per year)
- Whether off-grid or grid-tied makes more financial sense
- Battery bank sizing for energy independence
→ Check Canada's Electricity Rates by Province to calculate your potential savings and determine if solar makes financial sense in your area.
Solar Sweet Spot: Provinces with rates above 15¢/kWh typically see payback periods of 8-12 years, making solar an excellent long-term investment.
Complete Your Off-Grid Planning
Battery capacity calculations are just one piece of the puzzle. Here's your full off-grid planning checklist:
- ✓ Calculate battery capacity (you're here!)
- → Know your electricity rates – See how much you're currently paying and potential savings
- → Size your solar array – Match panel output to your daily energy needs
- → Calculate payback period – Determine ROI based on your province's electricity rates
- → Size your charge controller – Ensure proper battery charging from solar panels
Did You Know? In high-rate provinces like Alberta (25.8¢/kWh), Saskatchewan (19.9¢/kWh), or the territories (35-41¢/kWh), off-grid solar systems pay for themselves 40-60% faster than in low-rate provinces like Quebec or Manitoba.
More Tools & Resources
Looking for more ways to plan your off-grid solar system? Check out our complete collection of calculators and planning tools: