Charging Time Calculator

Find out how long it takes to fully charge a battery. Enter the battery capacity, your charger’s output and the charging efficiency for an instant estimate — perfect for phones, laptops, power banks and electric vehicles.

Battery capacity (mAh)

Charger output (mA)

Charging efficiency (%)

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Estimated charging time

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In decimal hours

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In days

Real charging slows down near full — most devices charge the last 20% more slowly to protect the battery, so treat this as a best-case estimate.

How to Use

Enter the battery capacity in mAh — printed on the battery or in the manual.
Enter your charger’s output current in mA (2000 mA equals 2 A).
Set the charging efficiency — 85% is a sensible default.
Read the estimated charging time instantly.

Key Features

Charging time estimate from capacity, charger output and efficiency.
Results in hours and minutes, decimal hours and days.
Adjustable efficiency to match real-world losses.
Live recalculation as you type.
Private — everything runs in your browser.

FAQs

Why is charging efficiency not 100%?

Some energy is always lost as heat in the charger, the cable and the battery chemistry itself. Most setups land between 75% and 90% efficient.

Why does the last part of charging take longer?

Modern batteries charge in two stages: fast constant-current charging up to about 80%, then slower constant-voltage charging to top up safely. The calculator gives a best-case figure.

Will a more powerful charger always charge faster?

Only up to the limit your device accepts. A phone that draws 2 A will not charge any faster on a 5 A charger — check your device’s maximum input.

Can I use it for electric vehicles?

Yes — convert the battery size to mAh and the charger output to mA first (1 kWh at 400 V is roughly 2,500,000 mAh), though EV charging curves make the estimate rougher.