For power bank capacity, most people do well with 10,000–20,000 mAh; match it to your devices and travel needs.
What mAh Means And Why It Matters
Milliamp-hours (mAh) describe how much charge a battery can store. Bigger numbers mean more total energy on board, which translates into more phone or tablet recharges before you need a wall outlet. Real runtime also depends on the battery inside your device, conversion losses in the pack, and how you use the gadget during charging.
Smartphones often sit between 3,000 and 5,000 mAh, while big phones push past 5,000 mAh. Small tablets start near 7,000 mAh and many laptops use packs measured in watt-hours. That range sets a baseline for picking a bank that gives you one, two, or several full top-ups.
Choosing How Much mAh For A Power Bank: Real-World Picks
Here’s a quick guide that maps common devices to sensible portable charger sizes. Use it as a starting point, then fine-tune with the calculator below.
| Device Type | Typical Device Battery | Good Bank Size |
|---|---|---|
| Small Phone | 3,000–3,500 mAh | 5,000–10,000 mAh (1–2 charges) |
| Standard Phone | 4,000–5,000 mAh | 10,000–20,000 mAh (2–3 charges) |
| Large Phone/Phablet | 5,000–6,000 mAh | 15,000–20,000 mAh (2–3 charges) |
| Compact Tablet | 6,000–8,000 mAh | 20,000 mAh (1–2 charges) |
| Full-Size Tablet | 8,000–12,000 mAh | 20,000–26,800 mAh (1–2 charges) |
| USB-C Laptop* | 35–65 Wh pack | 20,000–30,000 mAh (partial to 1 charge) |
*Laptop results depend on wattage draw and whether the bank supports the right USB-C power profile.
Fast Answer By Scenario
Daily Carry
If you just need a safety net for a long commute or a busy workday, a slim 5,000–10,000 mAh stick is a sweet spot. It’s enough for one full phone refill or two light top-ups.
Weekend Trips
For two or three days away, step up to 10,000–20,000 mAh. You’ll cover two or three full phone charges, plus a small tablet boost, without hunting for an outlet every night.
Family Or Multi-Device Days
When several phones, earbuds, and a tablet need help, 20,000–26,800 mAh keeps everyone happy. Pick a model with two or three ports.
Work Travel With A USB-C Laptop
You’ll want capacity plus the right power output. Look for 20,000–30,000 mAh and USB-C PD that matches your charger brick. A 45 W notebook needs a bank that can sustain 45 W or more.
How To Size It Properly (With A Simple Formula)
To plan with more precision, estimate the number of phone refills you need, then account for conversion losses. Portable chargers convert a 3.7 V internal cell to 5 V or higher for USB-C PD, and some energy is lost along the way.
The Handy Rule
For phones, assume you’ll get about 60–70% of the labeled mAh as usable. A 10,000 mAh bank often delivers about 6,000–7,000 mAh to a phone battery over a full cycle.
Quick Math
To convert between mAh and watt-hours, use: Wh ≈ (mAh × 3.7) ÷ 1,000. That 26,800 mAh favorite works out to about 99 Wh, which matches common airline limits for carry-on batteries.
Travel Rules And Safe Limits
Air travel adds one more check: where you can pack the battery and how big it can be. Portable chargers must ride in cabin bags, not in checked luggage. That rule protects baggage holds from the small chance of a cell fault going unnoticed.
Many regulators cap spare lithium-ion cells at 100 watt-hours without special approval, which is why you often see banks in the 20,000–26,800 mAh range. Some carriers allow two spares up to 160 Wh with approval, carried on, never checked.
For the official wording, read the
TSA power bank page
and the
IATA lithium battery guidance.
Charging Speed And Ports Matter Too
Capacity answers “how many times,” but speed answers “how fast.” USB-C Power Delivery (PD) lets your phone or laptop request higher voltages and currents. A bank rated for 30 W can fast-charge many phones and small tablets. Units marked 45 W or 65 W better match thin-and-light notebooks on many models.
Port mix also matters. One high-power USB-C port is handy for a laptop. A second USB-C keeps your phone topped up at the same time. A legacy USB-A is helpful for older cables. Many models today share power across ports, so the headline wattage may drop when two or three devices are connected.
Weight, Size, And Real-World Trade-Offs
More energy means more cells, and that means more grams in your bag. Slim 5,000 mAh sticks can weigh under 150 g. Compact 10,000 mAh packs hover near 200–250 g. Step to 20,000 mAh and you’ll carry 350–450 g. 26,800 mAh banks can approach half a kilogram. Decide what you’re willing to carry all day, then pick the smallest pack that meets your plan.
Pocket shape matters too. Rounded edges and non-slip shells make a bank easier to hold with your phone. An integrated cable saves space, while a short external cable gives flexibility across devices.
Quality And Safety Features To Look For
Good designs include a battery management system that watches voltage, current, and temperature. Look for clear wattage labels on each port, a percent-style charge readout, and a stable USB-C output under load. Protections like over-current shutoff, short-circuit protection, and cell balancing are table stakes from reputable brands.
Real Picks By Use Case
Commuter And Student
Carry a slim 10,000 mAh model with one USB-C PD port. It’s light, fits next to a phone, and takes the edge off long days. If your phone supports fast input, pick a bank that recharges itself at 18–30 W so a coffee break tops it up.
Weekend City Break
Go with 20,000 mAh and two USB-C ports. You’ll run maps, photos, and social apps without meter anxiety, and a second port lets a travel buddy share a boost.
Frequent Flyer
Pick a 26,800 mAh unit labeled near 99 Wh with a printed Wh rating on the case. Two USB-C ports with 65 W shared output cover a notebook and phone on layovers. Keep it in your cabin bag and never check it.
Parent With Multiple Devices
Choose 20,000–26,800 mAh with at least three outputs. A mix of two USB-C and one USB-A keeps kids’ tablets, headphones, and a parent phone alive during road trips or sports days.
Outdoor Day Hike
A rugged 10,000–15,000 mAh model with an IP-rated shell keeps weight down while still covering nav and photos. Skip built-in flashlights that drain the pack; carry a tiny headlamp instead.
Creator With Camera Gear
A 20,000 mAh bank that supports both standard PD and low-current trickle modes handles camera batteries, gimbals, and mics without tripping port protection.
How Long Will It Last Between Charges?
Two specs control the answer: the energy inside the bank and the power your device draws while filling. A phone sipping at 10–15 W will drain a 10,000 mAh pack slower than a laptop pulling 45–65 W. If you want all-day laptop help, move up to a higher-capacity model and match the PD wattage to your charger brick.
mAh To Wh Quick Reference (Nominal 3.7 V)
| mAh Label | Voltage For Calc | Approx Wh |
|---|---|---|
| 5,000 mAh | 3.7 V | 18.5 Wh |
| 10,000 mAh | 3.7 V | 37 Wh |
| 20,000 mAh | 3.7 V | 74 Wh |
| 26,800 mAh | 3.7 V | 99 Wh |
| 30,000 mAh | 3.7 V | 111 Wh |
Checklist Before You Buy
Match Capacity To Your Plan
Pick the smallest bank that covers your next day or trip with a cushion, not a bulky brick you’ll leave at home. If you bounce between desk and meetings, 10,000 mAh is often perfect. If you live on maps and media, 20,000 mAh hits a sweet spot.
Confirm PD Wattage
Read the fine print on both the bank and your device’s charger. Phone PD often peaks at 20–30 W. Many thin laptops settle at 45 W. Some creative notebooks want 65 W or more. A mismatch may stop fast-charging.
Look For Input Speed
You’ll recharge the bank often, so a fast input saves time. USB-C input at 20–45 W refills a 10,000–20,000 mAh pack in a couple of hours with the right wall charger and cable.
Check Cables And Labels
Use good USB-C cables rated for the wattage you need. Clear Wh and mAh labels on the case help at security checkpoints and during warranty claims.
Bottom Line Recommendation
If you want one take-anywhere pick for phones, choose 10,000–20,000 mAh with USB-C PD. If you carry a thin laptop, jump to 20,000–26,800 mAh with 45–65 W output. Travelers should keep banks in cabin bags and stay under the common 100 Wh cap. Match ports and wattage to your devices and you’ll charge faster, carry less, and stay powered through busy days.