The 1% panic
Phone dies at the gate, boarding pass is a screenshot, and the only outlet has a queue.
What size power bank?
Tell us your devices and your hours away from an outlet. Get the exact size to pack in mAh and Wh, the phone charges it gives, and whether it flies carry-on.
Free No email, no app, no math. It runs in your browser.
What size power bank do I need?
For most travelers, 10,000 mAh covers one phone for a full day, 20,000 mAh handles a phone plus a tablet, and 26,000 mAh keeps a laptop and phone going through a long work day. At about 96 Wh, 26,000 mAh is the largest single bank you can fly in a US carry-on without airline approval, because it stays under the FAA 100 Wh limit. Size yours exactly below.
| Power bank | Energy | Phone charges | Good for | Carry-on |
|---|---|---|---|---|
| 5,000 mAh | ~18.5 Wh | ~0.9 | One quick top-up, short outing | Yes |
| 10,000 mAh | ~37 Wh | ~1.7 | One phone, full travel day | Yes |
| 20,000 mAh | ~74 Wh | ~3.5 | Phone plus tablet, long-haul | Yes |
| 26,000 mAh | ~96 Wh | ~4.5 | Laptop plus phone, full work day | Yes, largest single bank |
Charges assume a typical 15 Wh phone battery and about 70% real-world delivery. The 100 Wh carry-on limit is roughly 27,000 mAh at the 3.7 V cell rating.
Your number
One recommended capacity in mAh and Wh, how many phone charges that is, and a clear carry-on flag.
20,000mAh
~74 Wh, about 3.5 phone charges
Example: one phone and a tablet, ten hours unplugged
- Sums each device battery, then adds real-world loss.
- Rounds up to a common 5k, 10k, 20k, or 26k bank.
- Under 100 Wh flies in your carry-on, no approval needed.
How the math works
Your devices
We sum a typical battery for each one: about 15 Wh a phone, 30 Wh a tablet, 55 Wh a laptop.
15 30 55
Your hours
Every 12 hours away from an outlet, we add one full top-up, because phones and laptops do not last forever.
+1top-up per 12 h
The headroom
We add 30% for real-world charging loss, round up to a common bank, then check it against the 100 Wh carry-on limit.
+30%real-world loss
Battery fails we all know
The dead-laptop layover
Brought a tiny power bank that tops up the phone but never touches the laptop.
The checked-bag mistake
Packed the power bank in checked luggage, then learned at the desk that lithium has to ride with you.
Quick examples
Tap a trip to load it into the calculator. Real kits, sized in your browser.
Why carry-on only
Lithium power banks have to fly with you, not in the hold. The size you pick keeps you under the airline approval line.
Power banks and spare batteries
On US flights the FAA requires lithium power banks and spare batteries in your carry-on, never checked luggage. Up to 100 Wh is fine; 101-160 Wh needs airline approval.
Charging cables and bricks
Cables, wall chargers, and multi-port USB bricks can go in either bag, but keeping them in one carry-on pouch speeds up TSA screening of loose electronics.
Laptops and large electronics
At US TSA checkpoints, laptops and tablets usually come out of the bag, so keep their chargers bundled separately to grab them fast.
The 100 Wh limit is about 27,000 mAh. Every size this tool recommends stays under it, so a single bank needs no airline approval.
Source: FAA PackSafe lithium batteries and TSA portable chargers .
Common questions
What size power bank do I need for travel?
It depends on your devices and how long you are away from an outlet. One phone for a day usually needs about 10,000 mAh, a phone and a tablet about 20,000 mAh, and a laptop and a phone for a full day about 26,000 mAh. The calculator sums a typical battery for each device, adds one full top-up for roughly every 12 hours unplugged, adds 30% for real-world charging loss, then rounds up to a common bank size.
How big a power bank can I take on a plane?
On US flights the FAA requires lithium power banks in your carry-on, never checked luggage. Up to 100 Wh is allowed with no airline approval, which is about 27,000 mAh at the usual 3.7 V rating. From 101 to 160 Wh you need airline approval. Every size this tool recommends stays under 100 Wh, so a single bank needs no approval.
How many phone charges does a 20,000 mAh power bank give?
About three to four full charges for a typical phone. A 20,000 mAh bank holds about 74 Wh and delivers roughly 50 Wh after real-world charging loss, while a typical phone battery is about 15 Wh.
Is the power bank calculator free and private?
Yes. There is no email, no account, and no sign up. The whole calculation runs in your browser and nothing is sent anywhere or stored.
Packing the pouch too?
Upload one photo of your cable pouch and get a readiness score, an organization grade, and three quick fixes.