mAh to Wh Converter

mAh to Wh Calculator: The Ultimate Guide to Converting Battery Capacity

Have you ever found yourself shopping for a new power bank or laptop battery, staring at a confusing jumble of numbers? One device boasts a massive 20,000mAh capacity, while another is listed as 74Wh. Which one actually holds more power? How long will it run your devices? This common confusion arises because battery capacity is often measured in two different units: milliamp-hours (mAh) and watt-hours (Wh).

For engineers, tech enthusiasts, frequent travelers, and everyday consumers, understanding the difference and being able to convert between these units is crucial. Manually calculating this conversion can be confusing and, if done incorrectly, can lead to buying the wrong product or even violating airline regulations.

This is where our mAh to Wh calculator comes in. This guide will eliminate the confusion by providing you with the tools and knowledge to understand and convert battery capacity like a pro. We will break down what mAh and Wh truly represent, reveal the critical role of voltage in the conversion, provide step-by-step examples, and show you how a dedicated calculator makes the process effortless.

Demystifying Battery Units: What Are mAh and Wh?

Before you can convert between them, it’s essential to understand that mAh and Wh measure two fundamentally different—though related—concepts.

What is a Milliamp-Hour (mAh)?

A milliamp-hour (mAh) is a unit of electric charge. It represents the amount of charge a battery can deliver over a specific period. The name itself breaks it down:

• Milli-: One-thousandth.

   

• Amp (Ampere): The base unit of electric current.

   

• Hour: A unit of time.

   

So, a 1mAh battery can deliver a current of 1 milliamp for 1 hour. A 5,000mAh smartphone battery can, in theory, deliver 5,000 milliamps of current for one hour, or 500mA for 10 hours, or 100mA for 50 hours.

Analogy: Think of mAh as the number of drops of water in a tank. It tells you the quantity of “stuff” (electric charge) stored inside, but it doesn’t tell you anything about the pressure that “stuff” is under.

You will most often see mAh ratings on smaller batteries, such as those in smartphones, power banks, headphones, and cameras.

What is a Watt-Hour (Wh)?

A watt-hour (Wh) is a unit of energy. This is the most important distinction. Energy is the true measure of the total work a battery can do. It’s calculated by multiplying power (in watts) by time (in hours).

• Watt: A unit of power (the rate of energy transfer).

   

• Hour: A unit of time.

   

A 30Wh battery can power a 30-watt device for one hour, or a 5-watt device for six hours.

Analogy: If mAh is the number of water drops, then a watt-hour is like the total potential work the water in the tank can perform. To know this, you need to know not only the number of drops (charge) but also the pressure they are under (voltage). This is why Wh is a more complete and universal measure of a battery’s energy capacity.

You will typically see Wh ratings on larger battery packs, such as those for laptops, drones, electric skateboards, and portable power stations.

The Conversion Formula: The Critical Role of Voltage

So, how do you bridge the gap between charge (mAh) and energy (Wh)? The missing link is voltage (V).

Voltage is the “pressure” in our water tank analogy. It is the electrical potential difference that pushes the current through a circuit. Without knowing the voltage of a battery, it is mathematically impossible to determine its energy capacity in watt-hours from its mAh rating alone.

The mAh to Wh Formula Explained

The formula to convert milliamp-hours to watt-hours is simple and elegant. It combines the charge (mAh) and the voltage (V) to calculate the energy (Wh).

The Formula:

Wh=1000mAh×V

Let’s break down why this formula works:

1. mAh × V: When you multiply the charge in milliamp-hours by the voltage, you are calculating the energy in a unit called milliwatt-hours (mWh).

2. / 1000: Since there are 1,000 milliwatt-hours in one watt-hour (just as there are 1,000 millimeters in a meter), this final step converts the result into the more standard and useful unit of watt-hours.

    

This formula is the engine behind our calculator and the key to making accurate comparisons between batteries.

How to Convert mAh to Wh: A Step-by-Step Guide

While using our calculator is the easiest method, understanding how to perform the conversion manually is empowering.

Manual Conversion Walkthrough

Step 1: Find the Milliamp-Hour (mAh) Rating. This is usually the most prominent number printed on power banks, smartphone batteries, and other small electronic devices.

Step 2: Find the Battery’s Nominal Voltage (V). This can be the trickiest part. The voltage is not always advertised as clearly as the mAh rating. Look for text printed on the device or battery casing that says “V,” “Volts,” or “Nominal Voltage.”

• For USB Power Banks and Smartphones: The vast majority of internal lithium-ion cells have a nominal voltage of 3.6V or 3.7V. If no other voltage is listed, using 3.7V is a safe and standard assumption for these devices.

   

• For Laptops and Drones: These devices often use multiple battery cells connected in series, resulting in higher voltages like 7.4V, 11.1V, 14.8V, or even higher. It is crucial to find the specific voltage listed on the battery pack.

   

Step 3: Apply the Formula. Plug the mAh and Voltage values into the formula: Wh = (mAh × V) / 1000.

Example 1: Converting a Power Bank’s Capacity

Let’s take a common 20,000mAh power bank.

• mAh: 20,000

• Voltage (V): We’ll assume a standard 3.7V nominal cell voltage.

Wh=100020,000 mAh×3.7 V=100074,000 mWh=74 Wh

So, a 20,000mAh power bank holds 74 watt-hours of energy.

Example 2: The “Aha!” Moment – Converting a Drone Battery

Now, let’s look at a high-performance drone battery with a rating of 5,000mAh. At first glance, this seems much smaller than the power bank. But let’s check the voltage. This type of battery often has a higher voltage, for instance, 14.8V.

• mAh: 5,000

• Voltage (V): 14.8V

Wh=10005,000 mAh×14.8 V=100074,000 mWh=74 Wh

This is the critical insight: The 5,000mAh drone battery contains the exact same amount of energy as the 20,000mAh power bank. The drone battery delivers its charge at a much higher “pressure” (voltage), which is why comparing mAh alone is so misleading. This demonstrates why converting to watt-hours is the only true way to compare battery capacity.

mAh to Wh Conversion Chart: A Quick Reference

For quick estimates, here is a conversion table for devices using a standard 3.7V nominal voltage.

The Easiest Method: Using Our mAh to Wh Calculator

While the manual calculation is straightforward, our mAh to Wh calculator is designed to provide instant and error-free results.

Why use the calculator?

• Accuracy: Eliminates the risk of manual math errors.

• Speed: Get your answer in seconds without having to remember the formula.

• Convenience: The simple interface makes the process painless.

How to Use the Calculator:

1. Enter the capacity of your battery in the “Milliamp-hours (mAh)” field.

2. Enter the nominal voltage of your battery in the “Voltage (V)” field.

3. The result in Watt-hours (Wh) appears instantly. No buttons to press, no waiting.

It’s the simplest and most reliable way to get the information you need.

Real-World Applications: Why This Conversion Matters

This isn’t just an academic exercise. This conversion has critical, practical applications.

Air Travel: FAA/TSA Battery Regulations

This is perhaps the most important real-world use case. Aviation authorities like the FAA and TSA have strict rules about the size of lithium-ion batteries you can bring on a plane. These rules are based on watt-hours.

• Under 100Wh: Batteries under 100Wh can be carried in your carry-on luggage without special permission. This covers most phones, power banks, and laptops.

   

• 100Wh to 160Wh: You can typically carry up to two of these larger batteries, but you must get airline approval first.

   

• Over 160Wh: These batteries are generally forbidden on passenger aircraft.

So, is your 20,000mAh power bank safe to fly with? As we calculated, it’s 74Wh—well under the 100Wh limit. You’re good to go. What about a massive 30,000mAh power bank?

Wh=100030,000 mAh×3.7 V=111 Wh

At 111Wh, this battery falls into the 100-160Wh category and would require you to check with your airline before flying. Using the mAh to Wh conversion is essential for travel compliance.

Comparing Devices and Making Smart Purchases

You’re trying to choose between two portable power stations. One is listed as 40,000mAh, and the other is 150Wh. Which is better?

Let’s convert the first one. Assuming a 3.7V nominal voltage:

Wh=100040,000 mAh×3.7 V=148 Wh

Now you have an apples-to-apples comparison. The 150Wh power station holds slightly more energy than the 40,000mAh (148Wh) one.

Frequently Asked Questions (FAQ)

Q: Can I convert mAh to Wh without knowing the voltage? A: No, it is mathematically impossible. Voltage is a required variable in the energy calculation (Energy = Charge × Voltage). Any website or tool that claims to convert without voltage is making an assumption about the voltage (likely 3.7V).

Q: What is a typical voltage for a USB power bank or smartphone? A: The internal lithium-ion or lithium-polymer cells are almost always rated at a nominal voltage of 3.6V or 3.7V. If no voltage is printed on the device, using 3.7V is the industry-standard assumption for the conversion.

Q: Is a higher mAh rating always better? A: Not necessarily. As our drone battery example showed, a lower mAh battery at a higher voltage can hold the same or even more energy (Wh) than a higher mAh battery at a lower voltage. Converting to Wh is the only reliable way to compare the true energy capacity.

Q: How do I find my battery’s voltage? A: Carefully inspect the casing of the battery or the device itself. Look for small print that includes a number followed by a “V”. It may be labeled as “Voltage,” “Nominal Voltage,” or simply be listed next to the mAh rating.

Conclusion: Never Be Confused by Battery Ratings Again

The worlds of milliamp-hours and watt-hours no longer need to be confusing. By understanding the core difference—that mAh measures charge while Wh measures energy—and recognizing that voltage is the key that connects them, you can make informed decisions about the devices that power your life.

While you can always do the math yourself, our mAh to Wh calculator is designed to be your go-to tool for this task. It provides the speed, accuracy, and convenience you need to compare products, ensure travel compliance, and truly understand the power you hold in your hands.

Bookmark our calculator today. Empower yourself with knowledge and make battery capacity confusion a thing of the past.