mAh stands for milliampere-hour, and it measures how much electric charge a battery can store. Think of it like the size of a gas tank: a higher mAh number means the battery can power a device for longer before it needs recharging. A battery rated at 5,000 mAh can deliver 5,000 milliamperes of current for one hour, or 1,000 milliamperes for five hours, or 100 milliamperes for 50 hours.
How mAh Works in Practice
The math behind mAh is straightforward. Divide the battery’s capacity by the amount of current your device draws, and you get a rough estimate of runtime in hours. A 2,500 mAh battery powering a device that uses 500 mA gives you about 5 hours. A phone with a 5,000 mAh battery consuming an average of 200 mA per hour could theoretically run for 25 hours.
That word “theoretically” matters. Real-world battery life is always shorter than the simple calculation suggests. Screen brightness, wireless connections, processor-heavy apps, and background tasks all change how fast your device drains power. A phone playing a graphically intense game pulls far more current than one sitting idle, so the same 5,000 mAh battery might last 6 hours of gaming or 20 hours of light use.
Typical mAh Ratings by Device
Different devices carry wildly different battery sizes because their power demands vary just as much. Here’s what you’ll typically see:
- Wireless earbuds: 30 to 80 mAh per earbud, with the charging case holding 300 to 600 mAh
- Smartwatches: 200 to 500 mAh
- Smartphones: 4,000 to 6,000 mAh. The global average reached roughly 5,000 mAh in 2025, with phones packing 6,000 mAh or more becoming increasingly common
- Tablets: 7,000 to 12,000 mAh
- Laptops: often listed in watt-hours (Wh) instead, but typically equivalent to 40,000 to 80,000 mAh
- Portable power banks: 5,000 to 30,000 mAh
Why mAh Isn’t the Whole Story
A bigger mAh number doesn’t automatically mean better battery life. Two batteries with identical mAh ratings can perform very differently depending on the voltage they operate at. A 3,000 mAh battery running at 3.7 volts stores more total energy than a 3,000 mAh battery running at 1.2 volts. That’s why laptops and power banks sometimes use watt-hours (Wh) instead, which accounts for both capacity and voltage. To convert, multiply the mAh by the voltage and divide by 1,000: a 3,000 mAh battery at 3.7 volts holds 11.1 Wh.
The device itself also plays a huge role. A phone with a power-efficient processor and a lower-resolution display can outlast a phone with a larger battery but more demanding hardware. When comparing devices, mAh tells you how much fuel is in the tank, but not how efficiently the engine burns it.
What Reduces Your Battery’s Actual Capacity
The mAh number printed on your battery represents its capacity when brand new, under ideal lab conditions. Several factors chip away at what you actually get.
Temperature is one of the biggest. Cold weather temporarily reduces how much charge a battery can deliver, which is why your phone might die unexpectedly on a freezing day. Heat does longer-lasting damage, gradually degrading the battery’s internal chemistry so it holds less charge over time. Leaving your phone in a hot car or consistently charging it to 100% in warm environments accelerates this wear.
Age matters too. Lithium-ion batteries lose a small percentage of their maximum capacity with every charge cycle. After a couple of years of daily charging, a battery originally rated at 5,000 mAh might effectively hold only 4,000 to 4,500 mAh. This is why older phones don’t last as long on a charge even after a factory reset.
High discharge rates also reduce effective capacity. A device drawing heavy current from a battery will get slightly less total energy out of it than one drawing a small, steady trickle. Gaming drains not just faster but slightly less efficiently than reading an e-book.
mAh and Air Travel Rules
If you travel with portable batteries or power banks, mAh matters for a regulatory reason. The TSA and most international aviation authorities limit lithium-ion batteries to 100 watt-hours per battery in carry-on luggage. For a typical power bank operating at 3.7 volts, that 100 Wh limit translates to roughly 27,000 mAh. Most smartphone power banks fall well under this threshold, but larger portable chargers can exceed it.
Spare batteries and power banks that aren’t installed in a device must go in your carry-on bag, not checked luggage. If your power bank doesn’t have its capacity clearly labeled, security screeners may not allow it through.
Comparing Battery Chemistries
The type of battery chemistry affects how much capacity fits into a given size. Lithium-ion cells, the kind found in phones and laptops, average around 1,500 mAh per cell but pack that energy into a small, lightweight package. Nickel-metal hydride (NiMH) rechargeable batteries, commonly used in AA and AAA sizes, average around 2,200 mAh per cell but are physically larger and heavier. Lithium-ion wins on energy density, meaning more mAh per gram of weight, which is why it dominates portable electronics.
Standard alkaline AA batteries hold roughly 2,000 to 3,000 mAh but aren’t rechargeable, so comparing their mAh to a rechargeable battery’s rating only tells part of the story. A rechargeable NiMH AA at 2,200 mAh that lasts 500 charge cycles delivers far more total energy over its lifetime than a single-use alkaline at 2,500 mAh.