So, what does mAh mean exactly? In short, mAh stands for milliampere-hour. It is a unit of measurement that represents the amount of electrical energy a battery can hold-essentially, the size of its "gas tank." The higher the mAh number, the longer the battery can power a device before needing a recharge.
However, if you have ever bought a 10,000mAh portable charger expecting it to charge your 5,000mAh phone battery exactly twice, you have likely been disappointed. That is because the number printed on the box is only half the story. As we settle into 2026, understanding the nuance of voltage conversion, heat loss, and the new Qi2 wireless standards is critical to getting the gear that actually works for your adventures.
Whether you are looking to power a weekend hike or keep a laptop running during a flight, knowing how to read these specs will save you money and frustration. Before you invest in new gear, it helps to understand the tech, but if you just want our top tested recommendations, check out The Best Power Banks of 2026: Tested for Your Next Adventure. Let's strip away the marketing fluff and look at the real math behind your battery life.
Key Takeaways
⚡ Quick Summary
- Definition: mAh (milliampere-hour) measures electric charge capacity. Think of it as fuel tank capacity.
- The 2/3 Rule: Due to voltage conversion and heat loss, a power bank usually delivers only about 60-70% of its rated mAh to your device.
- Watt-Hours Matter: For air travel and laptops, look at Wh (Watt-hours), not just mAh. TSA limits carry-on batteries to 100Wh (approx. 27,000mAh).
- 2026 Standards: The average smartphone now packs 4,500-5,500mAh. A 10,000mAh bank is the minimum for a reliable full backup.
- Speed vs. Capacity: High mAh does not mean fast charging. Look for PD 3.1 or 140W output for speed.
Breaking Down the Acronym: What is a Milliampere-Hour?
Technically speaking, one milliampere-hour is one-thousandth of an ampere-hour. It describes the energy charge that a battery will hold and how long a device will run before the battery dies.
Think of electricity like water flowing through a pipe:
- Voltage (V): The water pressure.
- Amperage (A): The width of the pipe (volume of flow).
- Capacity (mAh): The size of the water tank.
If you have a device that consumes 100 milliamps (mA) of power and you run it on a 2,000mAh battery, it should theoretically last for 20 hours ($2000 / 100 = 20$).
However, in the context of modern electronics like the Anker 737 Power Bank or the latest iPhone 17, the relationship isn't linear because power consumption fluctuates wildly based on screen brightness, 6G connectivity, and processor load. Understanding mAh is the first step in sizing your gear for off-grid trips or long commute days.
The 'Marketing Lie': Why 10,000mAh ≠ Two 5,000mAh Charges
This is the most common complaint we see in user reviews. You buy a 10,000mAh power bank for your phone with a 5,000mAh battery. Logic dictates you should get two full charges, right? In reality, you usually get about 1.5 charges. Here is why.
1. Voltage Conversion (The 3.7V vs. 5V Gap)
Most lithium-ion battery cells inside power banks operate at a nominal voltage of 3.7V (or sometimes 3.85V for newer high-density cells). However, the USB standard output is typically 5V, 9V, or even higher for fast charging protocols like Power Delivery (PD).
To charge your phone, the power bank must boost the voltage from 3.7V to 5V. This conversion process requires energy.
2. Efficiency Loss (Heat)
No electronic circuit is 100% efficient. Energy is lost as heat during:
- The voltage boost inside the power bank.
- The resistance in the charging cable.
- The voltage reduction inside your phone (stepping that 5V back down to charge the phone's internal battery).
The Real Capacity Formula
To find the actual usable capacity of a power bank, use this formula:
$$ \text{Real Output (mAh)} = \frac{\text{Rated Capacity} \times 3.7V}{5V} \times 0.85 \text{ (Efficiency)} $$
Example: A 10,000mAh Power Bank
- Energy in Watt-hours: $10,000 \times 3.7 = 37,000 \text{mWh} (37Wh)$
- Output at 5V: $37,000 / 5 = 7,400 \text{mAh}$
- After heat loss (approx 15%): $7,400 \times 0.85 = \mathbf{6,290 \text{mAh}}$
So, a "10,000mAh" battery really only gives you about 6,300mAh of usable juice at standard speeds. If you are using super-fast charging (9V or 15V), the efficiency can drop even further due to higher heat generation.
Comparing Capacities: What Size Do You Actually Need?
In 2026, device batteries are larger than ever. The iPhone 17 Pro Max and Samsung S26 Ultra both push past 5,000mAh internal capacities. This means the old "lipstick-sized" 2,500mAh chargers of the past are now effectively paperweights.
Here is a breakdown of common power bank sizes and their realistic utility for modern adventure tech.
| Rated Capacity | Real-World Output (Approx) | Best Use Case | Recommended Product Type |
|---|---|---|---|
| 5,000 mAh | ~3,000 - 3,300 mAh | Emergency Top-up. Gets an iPhone 17 to about 60%. Ultra-portable for pockets. | Anker Nano Power Bank (MagSafe/Qi2) |
| 10,000 mAh | ~6,000 - 6,500 mAh | The Daily Driver. One full charge for a flagship phone plus some extra for earbuds. Good for day hikes. | Anker MagGo Power Bank |
| 20,000 - 26,800 mAh | ~12,000 - 17,000 mAh | Travel & Laptop. Charges a phone 3-4 times or a tablet once. TSA limit maxes out around here. | Anker 737 Power Bank (24k) |
| 40,000 - 50,000 mAh | ~25,000 - 32,000 mAh | Base Camp. Charges multiple devices for days. Heavy and usually NOT flight legal. | 50,000mAh Portable Charger (Generic/Rugged) |
For most users, the 10,000mAh to 20,000mAh range is the sweet spot between weight and utility.
Watt-Hours (Wh) vs. Milliampere-Hours (mAh): Knowing the Difference
While mAh is the marketing number everyone knows, Watt-hours (Wh) is the scientific number that actually matters, especially for travel.
- mAh measures electric charge (Volume).
- Wh measures electrical energy (Total Work).
Why Wh is Superior: mAh is useless if you don't know the voltage. A 10,000mAh phone battery and a 10,000mAh drone battery contain vastly different amounts of energy if the drone runs at 14V and the phone at 3.7V.
The TSA Rule
If you are flying, the FAA and TSA enforce a limit on lithium batteries in carry-on luggage. That limit is 100 Watt-hours (Wh).
To calculate Wh from mAh: $$ \text{Wh} = \frac{\text{mAh} \times \text{Voltage}}{1000} $$
Most 26,800mAh power banks are designed exactly to hit this limit: $26,800 \text{mAh} \times 3.7\text{V} / 1000 = \mathbf{99.16 \text{Wh}}$
This is why you see oddly specific numbers like 26,800mAh or 24,000mAh-they are maximizing capacity without getting your gear confiscated at security.
mAh and Charging Speed: The C-Rate Factor
A huge misconception is that more mAh equals faster charging. It does not. Capacity (mAh) is how long it lasts; Output (Watts) is how fast it fills your device.
However, there is a technical link called the C-Rate. Larger batteries generally can discharge at higher rates safely.
- Standard Power Banks: Might have 20,000mAh but only output 15W. Good for phones, useless for laptops.
- Performance Power Banks: Like the Anker 737, boast 24,000mAh and can output 140W. This allows them to charge a MacBook Pro 16" while you are editing video in the field.
In 2026, look for "PD 3.1" or "Qi2 Certified" on the packaging. Qi2 is the new wireless standard that ensures efficient magnetic alignment (like MagSafe) for both Android and iOS, reducing the heat loss that usually plagues wireless charging.
Battery Health and Lifespan: Does mAh Degrade?
Yes. Every time you drain and recharge a lithium battery, it loses a tiny fraction of its capacity. This is called a cycle.
- Standard Li-ion: Typically rated for 300-500 cycles before dropping to 80% capacity.
- LiFePO4 (Lithium Iron Phosphate): Rated for 3,000+ cycles.
Most portable power banks still use standard Li-ion or Li-Polymer to keep weight down (LiFePO4 is heavy). If you use a 50,000mAh power bank daily, expect its effective mAh to drop noticeably after 18-24 months.
Pro Tip: To extend the life of your power bank, try not to store it at 0% or 100% for long periods. If you are storing your camping gear for the winter, leave the battery at roughly 50-60% charge.
Choosing the Right Power Bank for Your Needs
Buying a power bank in 2026 comes down to matching the mAh to your activity list. Here is our cheat sheet for the 'Geartor' audience.
1. The Ultra-Light Hiker / Urban Commuter
You need just enough juice to get home or call for help. Weight is the enemy.
- Target: 5,000mAh
- Features: Integrated USB-C connector or MagSafe/Qi2 snap-on.
- Pick: Anker Nano Power Bank (Great form factor for iPhone 17/16).
2. The Digital Nomad / Business Traveler
You need to power a laptop, phone, and maybe a tablet. You need high output (Watts) and legal capacity.
- Target: 20,000 - 24,000mAh
- Features: 65W+ output (ideally 100W+), numeric display for remaining time.
- Pick: Anker 737 Power Bank (The gold standard for laptop charging).
3. The Overlander / Camper
Weight doesn't matter; capacity is king. You are powering lights, fans, and phones for a weekend.
- Target: 40,000mAh+
- Features: Multiple ports, built-in flashlight, rugged casing.
- Pick: Portable Charger 50000mAh (Massive reserves for base camp).
Understanding what mAh means is the difference between carrying dead weight and having reliable power when you are miles from the nearest outlet. While the math of voltage conversion means you never quite get the full rated number, knowing the "2/3rds Rule" helps you plan effectively.
For most modern adventurers, a 10,000mAh unit covers daily needs, while 20,000mAh+ is essential for laptop users and longer trips. Don't get caught up in just the capacity number-pay attention to the Watt output to ensure your gear charges fast enough to keep up with you. Stay powered up, and we'll see you out on the trails.