The best capacity is not always the largest one. A smaller pack is easier to carry; a larger pack provides more charging cycles but adds weight and can approach airline battery limits.
Power-bank capacity comparison
| Rated capacity | Approximate nominal energy* | Best for | Recommended output |
|---|---|---|---|
| 10,000mAh | About 37Wh | Daily phone carry and short outings | 20–30W USB-C PD |
| 20,000mAh | About 74Wh | Multi-day phone use, tablets, handhelds | 45–65W when charging larger devices |
| About 27,000mAh | Near 100Wh | Laptop travel and maximum carry-on capacity | 65–140W, matched to the laptop |
*Illustrative estimates use a common 3.7V nominal cell voltage. Use the watt-hour figure printed by the manufacturer for travel decisions. Conversion losses mean usable USB output will be lower than the stored nominal energy.
The airline rule that matters
FAA guidance classifies power banks as spare lithium-ion batteries. They belong in carry-on baggage. Packs rated from 0 to 100Wh are generally allowed; 101–160Wh require airline approval, and packs over 160Wh are forbidden on passenger aircraft. Airlines may apply stricter limits.
Choose output as carefully as capacity
A high-capacity pack with a slow port can be frustrating. Phones may be satisfied with 20–30W, tablets and handhelds often benefit from 30–45W, and USB-C laptops commonly need 45–100W or more. Check the maximum single-port output and whether charging the bank while powering another device is supported.
Questions to ask before buying
- Is the watt-hour rating clearly printed on the product?
- Can one USB-C port deliver the wattage your laptop needs?
- How long does the power bank itself take to recharge?
- Does the included cable support the advertised output?
- Is the weight reasonable for daily carry?
Frequently asked questions
Can a power bank go in checked luggage?
FAA guidance treats power banks as spare lithium batteries and requires them in carry-on baggage, not checked baggage.
How do I convert mAh to Wh?
Divide milliamp-hours by 1,000 to get amp-hours, then multiply by the battery’s nominal voltage: Wh = V × Ah.
Is a 27,000mAh power bank airline-safe?
Many models are designed to remain near 100Wh, but travelers should use the exact Wh rating printed by the manufacturer and check their airline’s rules.