How to Calculate Power Bank Wh from mAh: TSA Flight Guide

Updated 2026-08-25 · Power Bank Guide

When you’re traveling by air, the first thing you need to know is whether your power bank meets the TSA/FAA 100 Wh carry‑on limit. To calculate power bank watt hours, you use the simple formula: Wh = (mAh ÷ 1000) × voltage. Most lithium‑ion cells are rated at 3.7 V, so a 20000 mAh pack translates to about 74 Wh – safely under the 100 Wh threshold.

How to Convert mAh to Wh for Travel Compliance

Take the capacity in milliamp‑hours, divide by 1,000 to get amp‑hours, then multiply by the nominal cell voltage (usually 3.7 V). For example:

• 20000 mAh ÷ 1000 = 20 Ah
• 20 Ah × 3.7 V = 74 Wh

Most airlines allow any battery under 100 Wh in carry‑on luggage, and you can carry up to two devices between 100 Wh and 160 Wh with airline approval. Anything above 160 Wh is prohibited on passenger aircraft. Always verify the latest rules with your carrier before you pack.

Real‑World Efficiency: From Wh to Actual Charges

Battery packs aren’t 100 % efficient. Internal circuitry, heat, and voltage conversion typically reduce usable energy to 60‑70 % of the rated Wh. Using a 74 Wh bank, you can expect roughly 44‑52 Wh of usable power.

Here’s how that translates to common devices (assuming average battery sizes):

• iPhone 17 (≈5 Wh): 8‑10 full charges
• Samsung Galaxy S24 (≈4.5 Wh): 9‑11 charges
• iPad Pro 12.9" (≈15 Wh): 2‑3 charges
• MacBook Air 13" (≈50 Wh): ~1 full charge (or 2 partial charges)
• Nintendo Switch (≈12 Wh): 3‑4 charges
• Steam Deck (≈45 Wh): 1‑2 charges

These numbers are estimates; actual results vary with screen brightness, usage intensity, and the efficiency of your charging cable.

What a 22.5 W USB‑C PD Bank Can Actually Power

USB‑C Power Delivery (PD) adds a programmable voltage range (5 V‑20 V) and higher current, allowing a 22.5 W bank to deliver up to 5 V × 4.5 A, 9 V × 2.5 A, or 15 V × 1.5 A. This is enough for most smartphones, tablets, and some thin‑and‑light laptops, but it won’t fully charge high‑power devices quickly.

Laptops: Ultrabooks that accept 15 V at 1.5 A (≈22.5 W) will charge, but expect a slow top‑up rather than a rapid fill. The MacBook Air (30 W charger) will trickle‑charge while in use.

Tablets & iPads: The iPad Pro 11" (30 W charger) will also receive a slower charge, roughly 5‑7 W, extending battery life but not replacing a wall adapter.

Gaming Hand‑Helds: The Switch in handheld mode draws about 7‑10 W, so a 22.5 W bank can keep it running for several hours. The Steam Deck, which typically uses a 45 W charger, will only receive a trickle charge and will drain faster than it refills.

Accessories: Earbuds, cameras, smartwatches, and other low‑draw gadgets (under 5 W) charge quickly and efficiently.

Why the INIU 20000 mAh Portable Charger Is a Good Travel Choice

The INIU 20000 mAh Portable Charger (Flight‑Safe) hits the sweet spot for most travelers. At ~74 Wh it stays well below the 100 Wh limit, and its 22.5 W USB‑C output can handle smartphones, tablets, the Switch, and even a thin‑and‑light laptop in a pinch. The included USB‑C cable and built‑in flashlight add convenience, and the compact form factor keeps it in a jacket pocket or backpack without bulk.

Because the bank’s efficiency is around 65 %, you can realistically expect about 45 Wh of usable energy—enough for multiple phone charges, a couple of iPad top‑ups, or a full Switch gaming session. Just remember that high‑power devices will charge slowly and may not reach 100 % before you land.

Practical Tips for Using Power Banks on a Plane

1. Carry‑on only: Stash the bank in your personal item; checked baggage rules differ and many airlines prohibit lithium batteries in the cargo hold.

2. Turn it off: Some airlines request that power banks be turned off or placed in airplane mode during takeoff and landing.

3. Use proper cables: A high‑quality USB‑C to USB‑C cable minimizes voltage drop and ensures the 22.5 W rating is met.

4. Monitor temperature: If the bank gets hot, pause charging. Overheating can reduce lifespan and may violate airline safety rules.

5. Know your device’s draw: Check your laptop or tablet’s power adapter rating. If it exceeds 22.5 W, the bank will only provide a trickle charge.

Bottom Line

Calculating power bank watt hours from mAh is straightforward, and staying under the 100 Wh TSA limit is essential for hassle‑free travel. A 22.5 W USB‑C bank like the INIU 20000 mAh Portable Charger can comfortably keep phones, tablets, earbuds, and even a Switch or thin laptop alive, though high‑power laptops will charge slowly. Always confirm the latest airline regulations and manage expectations around efficiency to get the most out of your portable charger.

FAQ

Can I bring a 20000 mAh power bank in my checked luggage?

No. Airlines typically require lithium‑ion batteries to be carried in the cabin, not in checked baggage, because of fire‑risk regulations.

Is a 22.5 W USB‑C output enough to charge a MacBook Pro?

It will provide a slow charge, but a MacBook Pro that normally uses a 61 W or 96 W charger will still drain faster than it refills.

How many full iPhone charges will a 74 Wh bank actually give?

Assuming 65 % efficiency, you get about 48 Wh usable. With an iPhone battery around 5 Wh, expect roughly 9‑10 full charges.