mAh stands for milliampere-hour, and it measures how much electric charge a battery can store. Think of it as a fuel tank rating: a higher mAh number means the battery holds more charge and can power a device longer before it needs recharging or replacing. A battery rated at 3,000 mAh can deliver 3,000 milliamps of current for one hour, or 1,500 milliamps for two hours, or 300 milliamps for ten hours.
How mAh Works in Practice
The unit breaks down simply. One milliampere-hour equals one thousandth of an ampere-hour (Ah), so 1,000 mAh and 1 Ah are the same thing. The “milli” prefix just makes the numbers easier to read for smaller batteries. You’ll see mAh on phone batteries, AA rechargeables, earbuds, and power banks. Larger batteries, like those in electric vehicles or home solar systems, use Ah or kWh instead because the numbers would otherwise stretch into the hundreds of thousands.
To estimate how long a battery will last, you divide its mAh rating by the average current draw of the device in milliamps. If your wireless headphones pull about 50 mA and the battery is rated at 500 mAh, you get roughly 10 hours of use. Real-world results will be shorter due to factors covered below, but the math gives you a useful ballpark.
Typical mAh Ratings Across Devices
Knowing common capacity ranges helps you compare products and spot marketing tricks. Here’s where most devices fall:
- Wireless earbuds: 40 to 80 mAh per earbud, with 300 to 600 mAh in the charging case.
- Smartwatches: 200 to 600 mAh.
- Smartphones: The global average sits around 4,900 mAh in 2025, with Chinese-market phones averaging 5,418 mAh. Phones with 6,000 mAh or more are increasingly common.
- AA rechargeable (NiMH): 600 to 3,000 mAh, depending on the cell.
- AA alkaline (disposable): 2,000 to 3,000 mAh.
- Portable power banks: 5,000 mAh on the small end, up to 30,000 mAh or more for laptop-charging models. A 10,000 mAh power bank will charge most phones about twice from empty.
For context, an iPhone 16 has a battery capacity of about 3,500 mAh, so a compact 5,000 mAh power bank can only fully charge it once. If you need to charge a laptop on the go, you’ll want at least 20,000 mAh, though those models are noticeably bulkier.
Why mAh Doesn’t Tell the Whole Story
mAh measures charge, not energy. Two batteries can have the same mAh rating but store very different amounts of usable energy, because mAh ignores voltage. A 3,000 mAh phone battery running at 3.7 volts stores about 11.1 watt-hours (Wh) of energy. A 3,000 mAh power tool battery running at 20 volts stores 60 Wh, roughly five times more energy.
The conversion is straightforward: multiply mAh by voltage, then divide by 1,000 to get Wh. This is why electric vehicles and laptops list capacity in Wh or kWh rather than mAh. When you’re comparing batteries that operate at the same voltage (two smartphones, for instance), mAh is a perfectly fair comparison. When voltages differ, you need Wh to make a meaningful one.
What Makes Real Battery Life Shorter Than the Rating
The mAh number on the label is measured under controlled lab conditions, typically by draining the battery at a slow, steady rate at room temperature. Your actual usage rarely matches those ideal conditions, and several factors eat into the advertised capacity.
Discharge rate matters. Drawing power quickly reduces the usable capacity. In testing on identical nickel-cadmium cells, increasing the discharge current from 100 mA to 500 mA dropped the effective capacity from 1.41 Ah to 1.22 Ah, a loss of about 13%. Lithium-ion cells handle high discharge better than older chemistries, but the effect still exists. If you’re gaming on your phone versus reading text, you’ll drain noticeably more of the battery’s total charge.
Cold temperatures hurt performance. A lithium-ion battery tested at zero degrees Celsius showed a 42% increase in internal resistance compared to room temperature, which significantly cuts the power it can deliver. Its measured capacity also dropped from 2.82 Ah to 2.68 Ah. This is why your phone dies faster on a cold winter day.
Age degrades capacity. Every charge cycle causes small, permanent chemical changes inside the battery. After a year or two of regular use, a lithium-ion battery may retain only 80 to 90% of its original mAh rating. Heat accelerates this aging, which is one reason keeping your phone out of hot cars helps preserve long-term battery health.
How to Use mAh When Shopping
When comparing two products in the same category, higher mAh generally means longer battery life, assuming the devices use similar processors and screens. But a phone with a 6,000 mAh battery and a power-hungry display could easily die before a more efficient phone with 4,500 mAh. The mAh rating is one piece of the puzzle, not the whole picture.
For power banks, pay attention to the difference between the cell capacity and the delivered capacity. A power bank rated at 10,000 mAh stores that charge at its internal cell voltage (usually 3.6 to 3.7V), but it outputs power at 5V through USB. The voltage conversion, plus heat losses, means you’ll typically get 60 to 70% of the advertised mAh into your phone. A 10,000 mAh power bank delivers closer to 6,000 to 7,000 mAh of usable charge at the output.
For rechargeable AA batteries, NiMH cells with higher mAh ratings (2,000+) are best for high-drain devices like game controllers or camera flashes. Lower-capacity NiMH cells (around 800 to 1,000 mAh) often hold their charge better during weeks of sitting idle, making them a smarter pick for TV remotes or clocks.