How to use the charging time calculator
- Enter battery capacity. Find the mAh rating in your phone's spec sheet or Settings. Most phones list 4,000–6,000 mAh.
- Enter charger power. Use the watt rating printed on your charger. If your phone supports less than the charger offers, add the phone's max input too.
- Set the charge range. Choose where you start and where you want to stop, for example 10% to 80%.
- Read the estimate. You get total time, a finish clock time and milestone times. Switch to Battery runtime to see how long a full charge lasts.
How phone charging time is calculated
The basic idea is simple: energy needed divided by charging power. Battery capacity in mAh is converted to watt-hours (Wh) by multiplying by the nominal voltage, so a 5,000 mAh battery at 3.85 V holds about 19.25 Wh. Divide by the power your phone really draws and you get an ideal charging time.
Why real charging takes longer
Three things stretch the ideal time. First, some energy is lost as heat, so efficiency is below 100%. Second, a phone only accepts as much power as its own charging circuit allows, no matter how powerful the charger. Third, lithium-ion batteries slow charging as they fill, with the biggest slowdown after about 80%. The typical taper option in this calculator models that slowdown.
mAh vs. Wh
mAh measures charge, not energy, so you cannot compare packs of different voltages by mAh alone. Wh is the fair comparison. It also matters for flights, where airline limits are normally stated in Wh.
Making your battery last
For tips on slowing battery wear, read the battery health guide and the fast charging guide. To see your device's live battery level and charging state, run the battery test.
Frequently asked questions
With a 25 W charger and a typical taper, a 5000 mAh phone usually takes about 1 hour 15 minutes to 1 hour 40 minutes from 10% to 100%. Use the calculator for your exact numbers.
Multiply the capacity in mAh by the nominal voltage and divide by 1000. For example 5000 mAh × 3.85 V ÷ 1000 = 19.25 Wh.
No. Your phone sets the maximum power it accepts. A 100 W charger will not charge a phone limited to 25 W any faster than a 25 W charger.
Lithium-ion batteries need lower current near full to avoid heat and stress. The phone reduces power automatically, which adds time but protects battery lifespan.
Runtime is battery energy in Wh multiplied by usable charge, divided by average power draw in watts. Actual draw varies with screen brightness, signal and apps.
Usually yes. Wireless charging has lower efficiency and many phones accept less power wirelessly, so set a lower efficiency percentage to model it.