Estimate how long it takes to charge a battery from any percentage. Supports phones, laptops, EVs, and power tools with efficiency accounting.
The Battery Charge Time Calculator estimates how long it takes to charge any battery — phone, laptop, power bank, electric vehicle, or power tool — from its current level to a target percentage. It accounts for charging efficiency, which means real charge times are always longer than the theoretical minimum.
Charging efficiency typically ranges from 80-90%, meaning 10-20% of the energy drawn from the wall is lost as heat. A 5,000 mAh phone battery charged at 10W takes longer than the simple math suggests because of this loss. This calculator includes the efficiency factor for realistic estimates.
With presets for common devices (smartphones, laptops, power banks, EVs, drills), adjustable current and target percentages, and a charge progress timeline, this tool answers the practical question: "When will my device be charged enough to use?". Check the example with realistic values before reporting. Use the steps shown to verify rounding and units. Cross-check this output using a known reference case.
Knowing exactly when your device will be charged helps you plan around charge times. This calculator accounts for real-world efficiency losses that simple division ignores. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain. Use this clarification to avoid ambiguous interpretation. Align this note with review checkpoints.
Wh Capacity = (mAh × Voltage) / 1,000 Energy Needed = Wh Capacity × (Target% - Current%) / 100 Actual Energy = Energy Needed / Efficiency Charge Time (hours) = Actual Energy / Charger Watts Charger Amps = Charger Watts / Voltage
Result: ~1h 11m (from 20% to 100%)
A 5,000 mAh phone battery at 5V has 25 Wh capacity. Charging 80% of that (20% to 100%) needs 20 Wh. At 85% efficiency, that\'s 23.5 Wh actual draw. At 10W, it takes about 2.35 hours — but real charging curves slow down above 80%.
No charger is 100% efficient. Energy is lost as heat in the charger, cable, and battery management system. Wired USB-C chargers typically achieve 85-93% efficiency, while wireless Qi chargers drop to 60-75%. This lost energy increases your electricity bill and generates waste heat.
USB-PD can deliver up to 240W, Qualcomm Quick Charge up to 100W, and Tesla Superchargers up to 250kW. Faster charging generates more heat and may reduce long-term battery capacity. This calculator helps you compare charge times across different charger wattages.
Lithium-ion batteries last longest when kept between 20-80% charge. Charging to 100% or draining to 0% regularly degrades capacity over time. Many modern devices offer "optimized charging" that slows the last 20% to reduce wear.
Charging efficiency (typically 80-90%) means some energy is lost as heat. Also, most devices slow charging above 80% to protect battery health, which this calculator\'s efficiency factor partially accounts for.
mAh (milliamp-hours) measures charge capacity at a specific voltage. Wh (watt-hours) measures total energy. Wh = (mAh × Voltage) / 1000. Wh is more universal for comparing different-voltage batteries.
Check the charger\'s label for output watts, or multiply its output voltage by output amps. A 5V/2A charger is 10W. A 20V/3.25A laptop charger is 65W.
Lithium-ion batteries use constant-current/constant-voltage (CC/CV) charging. Above ~80%, current tapers to prevent overcharging and heat damage, extending the last 20% significantly.
For most consumer devices, 80-90% is realistic. Wireless charging is less efficient (60-75%). High-quality wired chargers can reach 90-95%.
Yes. Use the EV preset or enter your battery capacity in Wh and your charger\'s power in watts. Keep in mind that EV charging rates often vary with state of charge.