Shopping & Money

Power Bank Calculator: How Many Times Will It Charge My Phone?

Free tool · Updated October 2, 2026 · By CouponTalk

Your result

Enter your measurements to see your result.

Quick answer

Power banks lose about 30–40% of their rated capacity in voltage conversion and heat. Charges ≈ power bank mAh × 0.65 ÷ phone battery mAh. A 10,000 mAh power bank charges a 5,000 mAh phone about 1.3 times, and a 20,000 mAh power bank about 2.6 times.

How to use this calculator

Pick your power bank's rated capacity.
Enter your phone's battery size (check its specs).
Choose an efficiency level.

Formula

Phone charges ≈ Power bank mAh × Efficiency ÷ Phone battery mAh

Watt-hours = mAh × 3.7 ÷ 1,000 (e.g. 20,000 mAh ≈ 74 Wh)

Results are estimates to help you plan. Confirm the final price, tax and offer terms at checkout.

Frequently asked questions

Why doesn't a 10,000 mAh power bank give two full charges?

Capacity is rated at the cell voltage (3.7 V), but phones charge at 5 V or more, and some energy is lost as heat. Usable capacity is about 60–70% of the rating.

Can I carry a power bank on a flight in India?

Power banks must go in cabin baggage, not checked luggage. Airlines generally allow up to 100 Wh (about 27,000 mAh) without approval; check your airline's rules.