5000mAh vs 10000mAh vs 20000mAh Power Banks: Which Capacity Do You Actually Need?

Perhaps you’ve bought a power bank before that promised “5 full charges” but barely managed two. Or maybe you lugged around a brick of a charger when a slim one would’ve done the job. The mAh number on the box tells part of the story, but not all of it.

Here’s how to cut through the marketing and pick the right capacity for how you actually use your phone.

Key Takeaways

• The advertised mAh capacity of a power bank is measured at the internal 3.7V battery voltage, so real-world usable capacity is typically around 55–70% of the stated value.
• A 10,000mAh power bank usually delivers about 6,000–7,000mAh of usable power, which is enough for roughly 1.5–2 full smartphone charges.
• 5,000mAh power banks are best suited for emergency or light use, while 20,000mAh models are better for travel, multi-device charging, and heavy usage.
• Charging speed depends on output wattage rather than mAh capacity, meaning a lower-capacity power bank with higher wattage can charge devices faster.
• Standard 5,000mAh, 10,000mAh, and 20,000mAh power banks are all below the 100Wh airline limit and are allowed in carry-on luggage.

Infographic by UGREEN. Please credit and link to the original article when used. Original article: https://uk.ugreen.com/blogs/power-bank/5000mah-vs-10000mah-vs-20000mah

What Does mAh Actually Mean?

mAh (milliamp-hours) measures how much energy a battery can store. Higher number = more stored power. Simple enough.

But here’s what most people don’t know: the advertised capacity is measured at the battery’s internal voltage (3.7V), not at the USB output voltage (5V). When the power bank converts the stored energy to charge your phone, you lose capacity due to voltage conversion and efficiency losses.

The reality:

• A 10,000mAh power bank delivers roughly 6,000-7,000mAh of usable power
• A 20,000mAh power bank delivers roughly 12,000-14,000mAh
• Expect roughly 55–70% of the advertised capacity in real-world use, depending on conversion efficiency and internal circuitry.

This is why your “10,000mAh” power bank doesn’t charge your 4,000mAh phone three times as you expected. It’s not a scam—it’s physics. Quality power banks with efficient circuitry get closer to 70%. Budget models often land around 60%.

Here’s a quick comparison table to make it easy.

*Estimates are approximate and vary based on device battery size, charging efficiency, and power bank output.

When are 5,000mAh Power Banks the Best Choice?

Best for: Light users, evenings out, “get me home” situations

A 5,000 mAh power bank gives you about one full smartphone charge—sometimes a bit less with larger phones like the Galaxy S24 Ultra (5,000 mAh) or iPhone 16 Pro Max (4,685 mAh).

What you get:

• Pocket-sized, often credit card thickness
• Lightweight (~100-150g)
• Quick to recharge

Ideal scenarios:

• Night out when you don’t want to carry a bag
• Emergency backup in your car’s glovebox
• Topping up wireless earbuds or a smartwatch
• Kids’ devices (enough for a top-up, not heavy)

Limitations:

• Won’t get you through a full day of heavy use
• Not suitable for tablets or laptops
• May need recharging frequently if used daily

Who should skip this size: Anyone who regularly drains their phone before getting home, travels frequently, or charges multiple devices.

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When are 10,000mAh Power Banks the Best Choice?

Best for: Most people, daily commuters, moderate users

The 10,000mAh capacity has become the default for good reason. With roughly 6,000-7,000mAh of usable power, you’re looking at 1.5-2 full smartphone charges—genuine peace of mind for a full day without the bulk of larger options.

What you get:

• Still reasonably portable (fits in a jacket pocket or small bag)
• Weight typically 180-300g
• Often, the best balance of price, capacity, and portability

Ideal scenarios:

• Long work days away from outlets
• Day trips and sightseeing
• Commuters with long journeys
• Charging phone + earbuds/watch during the day
• Business travellers on short trips

Why this is the “sweet spot” for most people: If you’re buying your first power bank or replacing an old one, this is usually the right choice. It covers the vast majority of daily use cases without weighing down your bag or emptying your wallet.

Limitations:

• Not enough for multi-day trips without recharging the power bank
• Won’t meaningfully charge a tablet or laptop
• Heavy users may still run out on very long days

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When are 20,000mAh Power Banks the Best Choice?

Best for: Frequent travellers, heavy users, multi-device households

When your plans extend beyond a single day, your power needs grow exponentially. A 20,000mAh power bank delivers roughly 12,000-14,000mAh of usable power—enough for 3-4 full smartphone charges.

What you get:

• Can partially charge tablets and some laptops (with USB-C PD)
• Enough to share power with travel companions
• Typically 350-500g (backpack weight, not pocket weight)

Ideal scenarios:

• Multi-day trips and weekend getaways
• Long-haul flights and airport layovers
• Camping and outdoor adventures (no outlet access)
• Charging multiple devices (phone + tablet + earbuds)
• Content creators and photographers in the field
• Family travel (charging multiple phones)

Important note on laptops: A 20,000mAh power bank with USB-C Power Delivery (45W–65W output) can partially charge or extend the runtime of some ultrabooks and lightweight laptops. It won’t fully charge a MacBook Pro 16", but it can extend your working time significantly. Check your laptop’s power requirements before relying on this.

Limitations:

• Too heavy and bulky for everyday pocket carry
• Takes longer to recharge the power bank itself (6-10 hours standard, faster with quick-charge input)
• Overkill for casual daily use

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Do Certain Power Banks Have Airline Restrictions?

Good news: all three sizes are flight-safe.

The rules from TSA, FAA, and IATA are consistent:

• Power banks must go in carry-on luggage (never checked bags)
• Under 100Wh: Allowed without approval
• 100-160Wh: Requires airline approval, limit of 2 per passenger
• Over 160Wh: Prohibited on passenger flights

How to calculate watt-hours: Wh = mAh × 3.7V ÷ 1000

• 5,000mAh × 3.7V = 18.5Wh ✓
• 10,000mAh × 3.7V = 37Wh ✓
• 20,000mAh × 3.7V = 74Wh ✓
• 27,000mAh × 3.7V = 99.9Wh ✓ (just under the limit)

You’d typically need a power bank over ~27,000mAh to approach the 100Wh threshold. In practice, airlines rely on the labeled watt-hour (Wh) rating when enforcing carry-on limits. Standard 5,000/10,000/20,000mAh power banks are all well within the limit—no paperwork needed.

How to Choose The Best Power Bank for Your Needs

Choose 5,000mAh if:

• You rarely drain your phone completely
• Portability is your top priority
• You just want emergency backup
• Budget is tight

Choose 10,000mAh if:

• You want all-day peace of mind
• You’re a daily commuter or office worker
• You charge one phone plus small accessories
• You want the best balance of size, capacity, and price

Choose 20,000mAh if:

• You travel frequently or take multi-day trips
• You’re often away from outlets for extended periods
• You charge multiple devices or share with others
• You need to top up a tablet or laptop occasionally
• Weight in a bag isn’t a concern

Other Factors Worth Considering

1. Output wattage matters too. Capacity tells you how much power is stored. Output wattage (W) tells you how fast it can deliver that power. A 20,000mAh bank with 10W output will charge your phone slowly. One with 22.5W or higher delivers fast charging.
2. Number of ports. If you charge multiple devices, look for 2-3 output ports. Some power banks let you charge devices while the bank itself recharges (pass-through charging).
3. Recharge time. Larger capacity = longer recharge time. A 20,000mAh bank might take 8-10 hours to fully recharge via standard USB. Models with fast input (18W+ USB-C) cut this significantly—some can reach 50% in under an hour.

FAQs

How many times will a 10,000mAh power bank charge my phone?

Expect 1.5-2 full charges for most modern smartphones (iPhone 16, Galaxy S24, Pixel 9). The advertised capacity drops by 30-40% due to voltage conversion and efficiency losses.

Is a 20,000mAh power bank allowed on planes?

Yes. At 74Wh, it’s well under the 100Wh limit for carry-on luggage. Just remember: power banks must go in your carry-on, never checked bags.

Does higher mAh mean faster charging?

No. Capacity (mAh) and charging speed (watts) are different things. A 5,000mAh power bank with 22.5W output can charge your phone faster than a 20,000mAh bank with 10W output.

How long does a 20,000mAh power bank last before needing to recharge?

Depends on usage. If you’re charging a smartphone once daily, it could last 3-4 days between recharges.

Why doesn’t my power bank charge my phone as many times as advertised?

The advertised mAh is measured at the battery’s internal 3.7V. When converting to 5V USB output, plus efficiency losses, you get roughly 60-70% of the stated capacity as usable power.

Can a 20,000mAh power bank charge a laptop?

Some can, if they have USB-C Power Delivery with 45W+ output. Check your laptop’s power requirements—ultrabooks typically need 45-65W, while larger laptops need more.

Match Your Power Bank Capacity to Your Lifestyle

The right power bank isn’t necessarily the biggest one, it’s the one that fits how you actually live. 5,000mAh for emergencies, 10,000mAh for daily use, 20,000mAh for travel and heavy users.

Don’t just look at the mAh number. Consider the weight you’re willing to carry, the output wattage for fast charging, and whether you’ll actually use all that capacity before you can recharge. UGREEN’s power bank range covers all three capacity tiers with clear specifications, efficient circuitry, and the output wattage to actually deliver fast charging, not just store power.