mAh vs Wh: A Simple Guide to Battery Life

When you're trying to figure out which battery pack is best, you'll often see two measurements: mAh and Wh. So, what's the simple answer? Watt-hours (Wh) give you a much better picture of a battery's total energy than milliampere-hours (mAh) ever could. If you want to know how long your device will actually last, Wh is the number to look at.

Why Watt-Hours Are a Better Measure Than mAh

Let's try a simple analogy. Think of a battery like a water bottle. The mAh rating tells you how much water the bottle can hold. But Wh, on the other hand, tells you how long you can actually drink from that bottle, because it also considers the pressure pushing the water out. In battery terms, that "pressure" is its voltage.

Because Watt-hours include voltage in their calculation, they measure the total energy a battery holds. This makes it the best way to compare any two batteries, no matter what size they are or what device they're for.

The Problem with Only Using mAh

If you only look at mAh, you can easily be misled. For example, a 10,000 mAh power bank for your phone (which runs at 3.7 volts) actually holds less total energy than a smaller 8,000 mAh power bank for a laptop (running at 12 volts). The laptop pack's higher voltage delivers more power, making its lower mAh rating a bit tricky.

Key Takeaway: Watt-hours (Wh) is the true measure of a battery's energy. It combines both capacity (mAh) and voltage (V) to give you a genuine apples-to-apples comparison between any two batteries.

This is exactly why airlines set their battery restrictions in Wh, not mAh. It's the universal language of energy storage. Understanding this difference is also helpful if you're trying to figure out an electric vehicle's real-world mileage, a topic that often comes up in guides for decoding electric scooter range.

Comparing mAh vs Wh at a Glance

To make it even clearer, here’s a simple breakdown of what each unit is really telling you.

By shifting your focus to Watt-hours, you can make smarter choices and ensure the battery you're buying actually has the power you need for your devices.

Understanding mAh and Its Limitations

When you glance at a battery's specs, the first number you usually see is its capacity in milliampere-hours (mAh). For a long time, this was the main number people looked at. Think of it as a small bucket that holds a certain amount of electricity.

Years ago, this worked just fine. Most smartphones and gadgets ran on batteries with a similar voltage, typically around 3.7V. In that environment, a bigger mAh number meant a longer-lasting device, plain and simple. A 4,000 mAh battery would reliably outlast a 3,000 mAh one because the "pressure" pushing the electricity out—the voltage—was the same.

Why mAh Can Be Misleading Today

But the tech world has changed. Today's devices, from powerful smartphones to beefy power banks and laptops, use all sorts of different voltages. This is where relying only on mAh gets you into trouble.

Comparing two batteries by mAh alone is like trying to figure out which car goes farther by only looking at the size of its gas tank. A huge truck with a 25-gallon tank seems way better than a tiny car with a 10-gallon tank, right? But if the truck gets poor mileage and the car is super-efficient, the smaller car might actually travel much farther on a full tank. Voltage is like that fuel efficiency—it determines how much real work the stored charge can actually do.

The Critical Flaw: Milliampere-hours (mAh) only measure electrical charge, not the total energy stored. Without knowing the voltage, the mAh value is just one piece of the puzzle and can give you a false sense of a battery's true capacity.

The Shift to a Universal Standard

This is exactly why the industry has been shifting to a better, more honest measurement. Back in the early days of portable electronics, mAh was simple and it worked. But as the market filled with devices using different battery types and voltages, Wh became the true global standard because it accounts for those voltage differences. In fact, over 75% of new electronics now list battery capacity in Wh.

Understanding this difference isn't just about nerding out over specs; it's key to taking care of your devices. To really get the most out of every charge and understand the ideas behind maintaining excellent battery health, you need to look past simple marketing numbers.

To get the full picture, it helps to understand the various battery and charging technologies that power our modern world. This knowledge lets you see what truly matters: the total available energy, not just the size of the "bucket."

How to Easily Convert mAh to Wh

Now that we know the key difference between mAh and Wh, let's get practical. The next step is learning how to convert between them. It’s surprisingly simple and lets you accurately compare any two batteries, no matter what the marketing says.

This little bit of knowledge puts you in control, letting you see the true energy capacity hidden behind the numbers. The good news? You don’t need to be a math whiz.

The Simple Conversion Formula

To figure out a battery's true energy in Watt-hours, you just need two pieces of information: the advertised mAh and the battery's voltage (V). You can usually find the voltage in the device specs or written in small print on the battery itself.

Once you have those numbers, you just use this simple equation:

Wh = (mAh × V) / 1000

That's it. You multiply the milliamp-hours by the voltage. Then, you just divide by 1,000 to turn it into the standard unit of Watt-hours. If you want to dive deeper into the math, our guide on converting amp-hours to watt-hours offers a more in-depth look.

This chart really brings the point home, visually showing how a battery with a lower mAh rating can actually hold more energy if its voltage is higher.

As you can see, voltage is a huge factor. A 10,000 mAh battery with a high enough voltage can easily pack more punch than a 20,000 mAh battery that runs at a lower voltage.

Real-World Conversion Examples

Let’s put this formula to work with some devices you probably have lying around. Seeing the math in action makes it crystal clear how misleading mAh can be on its own. This is essential for anyone trying to truly understand the mAh vs Wh relationship in the real world.

The following table shows you how to convert common mAh ratings into Wh for different devices, highlighting why voltage is so important in determining true battery energy.

Look at that. The MacBook's battery, with what seems like a small 6,688 mAh, actually holds three times more energy than the iPhone. It even has nearly 70% of the energy of the massive 20,000 mAh power bank, all because its voltage is more than double.

This is exactly why you can't trust mAh alone. By running this quick calculation, you can confidently compare any two batteries and know exactly which one packs more power.

Putting It All Together: Real-World Scenarios

Knowing the theory is great, but what really matters is how it works in the real world. Understanding mAh vs. Wh isn't just for tech geeks—it directly affects what you buy, how you travel, and even your safety. Let's walk through a few common situations where this knowledge is absolutely essential.

Imagine you're shopping for a new power bank. You see two options, both advertised with a big 20,000 mAh capacity, but one is way more expensive. Why? The cheaper one probably uses standard 3.7V battery cells, which adds up to 74 Wh of total energy. But the premium model, designed for laptops, might use 5V cells, giving it a much more impressive 100 Wh.

Even with the same mAh rating, that second power bank holds nearly 35% more actual energy. It can recharge your phone more times or keep a power-hungry laptop running for longer. This is a classic example of why focusing on Wh shows you the true power you're getting for your money. Our guide on how to use a power bank effectively can help you get the most out of every last drop of that energy.

Airline Regulations and Travel

The moment you start packing for a flight, the mAh vs. Wh difference suddenly becomes very important. Airport authorities like the TSA and FAA have strict rules about the batteries you can carry on a plane, and those limits are almost always stated in Watt-hours.

For most airlines, the hard limit for spare batteries is 100 Wh. That's the magic number you can bring without needing special permission. If you get airline approval, you might be able to carry up to two larger batteries, typically between 101 Wh and 160 Wh.

Trying to explain your 20,000 mAh power bank to a security agent is a losing battle. They don't care about mAh. They need to see the Watt-hour rating printed right there on the device. If it's missing, you're running the risk of it being taken away.

The Bigger Picture: Electric Vehicles

This whole concept gets much bigger when you look at things like electric vehicles (EVs). In the EV world, battery capacity is measured in kilowatt-hours (kWh), which is just 1,000 Wh. You'll never see an EV maker advertise battery size in mAh because the number would be huge and meaningless.

Total energy is the only thing that matters. Take Volkswagen's ID.7 Tourer, for example. It has a battery with around 77 kWh (or 77,000 Wh), which is what gives it such a good driving range. The push for bigger Wh batteries is a key reason EV popularity has grown so much. For example, Volkswagen Group is increasing global deliveries thanks to these improvements. It just goes to show that from a tiny power bank to a high-performance car, Watt-hours are the ultimate measure of energy.

Common Battery Myths Debunked

Navigating the world of battery specs can feel confusing. Many common beliefs we have about battery capacity are either old-fashioned or just plain wrong. Let's bust a few of the biggest myths so you can see a battery's true power.

This is where the whole mAh vs. Wh confusion can really trip you up. Once you understand what’s really going on behind the marketing, you can start evaluating batteries like a pro and make much smarter decisions.

Myth: A Bigger mAh Number Is Always Better

This is probably the most common—and most misleading—myth out there. A huge mAh figure looks impressive, but it does not guarantee more power or longer battery life. The real story depends entirely on the battery's voltage.

Take a 10,000 mAh power bank running at a standard 3.7V. Its total energy is 37 Wh. Now, consider a smaller 7,000 mAh battery pack built for a different device that operates at 5V. That one contains 35 Wh of energy. In this case, the battery with the smaller mAh number is almost just as powerful.

Fact: Watt-hours (Wh) are the only way to make a true apples-to-apples comparison. A battery with a lower mAh rating but a higher voltage can easily pack more total energy than one with a high mAh and low voltage.

Myth: Manufacturers Are Always Honest

It would be nice if they were, but unfortunately, some marketing can be intentionally vague. It's a classic move for certain brands to put a massive mAh number on the box while hiding the voltage in the fine print—or leaving it out altogether.

This tactic is designed to make a product seem more powerful than it actually is. Without knowing the voltage, that big mAh number is almost useless for comparing anything.

Here's how to stay sharp:

• Look for the Voltage: Always check the technical specs to find the voltage (V).
• Do the Math: Use the formula Wh = (mAh × V) / 1000 to find the real energy capacity.
• Be a Little Skeptical: If a manufacturer makes it hard to find the voltage, it could be a red flag.

By arming yourself with this simple bit of knowledge, you can see right past the flashy numbers and understand exactly what you’re buying.

Got More Questions About Battery Capacity?

Diving into battery specs can sometimes leave you with a few more questions. Let's clear up some of the most common ones that pop up when you're trying to figure out mAh vs. Wh.

Is 10,000 mAh a Big Deal for a Power Bank?

A 10,000 mAh power bank is a really popular choice for most people's daily needs. If we assume a standard 3.7V, that gives you 37 Wh of energy, which is usually enough to charge a modern smartphone two or even three times. It’s a solid option.

But remember, the total power a bank holds is all about its voltage. You should always try to find or calculate the Watt-hour (Wh) rating to know what you're really getting. You might find another power bank with a lower mAh but a higher voltage that actually offers more total juice.

What's the Real Battery Limit for Flying?

This is where knowing about Wh is absolutely essential for anyone who travels. Nearly all airlines follow the guidelines set by the FAA and TSA, which limit spare batteries to 100 Wh each in your carry-on bag.

If you get special permission from the airline beforehand, you might be able to bring up to two bigger batteries, somewhere between 101 Wh and 160 Wh. This is exactly why Wh has become the global standard for battery safety and travel rules.

So Why Do Phones Still Brag About mAh?

Honestly, using mAh is mostly a habit left over from old marketing. When smartphones first came out, their batteries all had very similar voltages, so mAh worked as a simple, good-enough way for people to compare battery life at a glance.

Even though it's not the best way to compare batteries today, the term has stuck around simply because everyone is used to it. But if you want to make a truly informed comparison, you’ll always want to look for the Wh rating.

When you understand the real energy in your batteries, you can start taking much better care of them. Chargie is a little guardian for your battery, helping you protect its long-term health by automatically managing how it charges. It stops the damage that happens when your phone sits at 100% all night long. You can extend your device's life and cut down on e-waste by learning more at https://chargie.org.