Charging Time Calculator
How long a phone, power bank or battery takes to charge — capacity, charger wattage and real-world efficiency included.
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The Honest Charging Math
Energy in the battery = mAh × voltage (phones use 3.7 V nominal): a 5,000 mAh phone holds 18.5 Wh. Time ≈ energy ÷ (charger watts × efficiency) — chargers lose 10-20% to heat and conversion, so the tool defaults to 85%. On a 25 W charger that 5,000 mAh phone computes to ~52 minutes for the bulk… but real full charges run longer because the last 20% is deliberately slow (constant-voltage taper protects the cell). Expect the computed time to cover 0→80%, then add roughly half again to reach 100%.
Power banks list mAh at 3.7 V too — a "20,000 mAh" bank at 18 W input needs ~5 hours. The charger and cable must both support the wattage: a 65 W GaN brick through a cheap 15 W cable charges at 15 W.
Frequently Asked Questions
Why does my phone charge slower than calculated?
Screen on, background sync, heat throttling and the 80%+ taper all stretch it. Charging in a cool spot with the screen off gets closest to the math.
Does fast charging damage the battery?
Heat is the real enemy, not watts per se. Modern phones manage the curve; avoiding hot environments and sustained 100% charge matters more than the charger rating.
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Charging Time Calculator