Battery Charging Time Calculator
Explore charging scenarios for phones and laptops. This model makes its assumptions visible rather than promising an exact finish time.
iTechVora Tools
Battery Charging Time Calculator
Explore an estimated charging window with explicit power and taper assumptions.
Free · No signup · Calculations run in your browser
Ready to calculate
How to use
Choose mAh or Wh, enter the current and target percentages and charger wattage, then open Advanced to enter the device charging limit. The default 25 W device limit is an example, not a detected specification. Use the battery’s nominal voltage if entering mAh.
Methodology
Battery energy = mAh × nominal voltage / 1,000, or the entered Wh directly. Available battery power = min(charger watts, device limit) × efficiency. Each overlapping charge phase adds time = battery energy × fraction charged / phase power.
This illustrative model uses 100% of available power for 0–50%, 65% for 50–80%, and 30% for 80–100%. The displayed window is 80–130% of the resulting modeled time, rounded outward to minutes. These factors and bounds are editorial assumptions, not manufacturer measurements or statistical confidence limits.
Worked example
With a 5,000 mAh, 3.85 V battery, a 45 W charger, a 25 W device limit and 85% efficiency, charging from 20% to 100% models about 78 minutes, displayed as an illustrative 62–101 minute window.
Limits and sources
A compatible charging protocol and cable are assumed. Temperature, device use, battery age and optimized charging can push the real time outside the window. Apple describes why charging slows at higher levels in its lithium-ion battery explanation; it does not validate the phase factors used here.
FAQ
Will a larger charger always charge faster?
No. The device’s supported power and the negotiated charging protocol limit what it can accept.
Why does the last 20% take longer?
Charging power typically tapers as the battery fills. Exact charging behavior varies by device and conditions.
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Methodology version 1 · Updated September 28, 2026.