Tech & Gadgets

Battery Charge Time Calculator: How Long to Charge Your Phone, Laptop or Power Bank

Free tool · Updated October 3, 2026 · By CouponTalk

Your result

Enter your measurements to see your result.

Quick answer

Charge time ≈ energy needed ÷ (charger power × efficiency). A 5,000 mAh phone battery stores about 19 Wh; from 20% to 100% it needs about 15 Wh. On a 25 W charger at about 80% efficiency that is roughly 45 minutes of full-speed charging, but charging slows above 80%, so expect about an hour. Phones only charge fast if both the charger and phone support the same standard.

How to use this calculator

Enter the battery capacity from the spec sheet.
Enter the charger wattage printed on it.
Set your current and target charge levels.

Example charge times

Estimates; charging slows above 80%
Device	Battery	Charger	About 0–100%
Phone	5,000 mAh (19 Wh)	18 W	1 h 50 min
Phone	5,000 mAh (19 Wh)	45 W	45 min
Laptop	60 Wh	65 W	1 h 35 min
Power bank	20,000 mAh (74 Wh)	18 W	about 7 h

Real times vary with temperature, cable and use while charging.

Frequently asked questions

Why does charging slow down near 100%?

Batteries charge at full speed until about 80%, then slow down to protect the cells.

Can I use a higher-watt charger?

Yes; the phone only draws what it supports, so a 65 W charger on a 25 W phone charges at 25 W.

How is mAh converted to Wh?

Multiply mAh by the battery voltage (about 3.85 V for phones) and divide by 1,000.

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