Battery Capacity and Runtime Calculator
Convert nominal battery charge and energy using battery voltage. Estimate constant-load runtime from usable capacity and conversion efficiency.
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Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Multiply rated amp-hours by nominal battery voltage for watt-hours, or divide rated watt-hours by nominal voltage for amp-hours. Apply usable capacity and output conversion efficiency before dividing by the constant output load.
Wh=Ah×V; runtime hours=Wh×usable fraction×efficiency/load watts
Worked example
10000 mAh at a nominal battery voltage of 3.7 V is 37 Wh. At 100% usable capacity, 90% conversion efficiency and a constant 10 W output load, estimated runtime is 3.33 hours.
Assumptions and input details
Use the nominal voltage associated with the rated battery charge, not an unrelated USB output voltage. Usable fraction is 0–100%; efficiency is positive up to 100%. Voltage is positive and load power is nonnegative. Zero load has no finite exhaustion time in this model, which omits self-discharge and idle draw. Capacity, voltage and efficiency are treated as constant averages. Temperature, battery age, cutoff voltage, discharge-rate effects and load peaks are not inferred. This is an energy estimate, not a charging procedure, pack design or guarantee of actual runtime.
References: Anker battery capacity units
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
SI prefixes are explicit: for example, milli means one thousandth, micro one millionth and kilo one thousand. Changing a unit changes the interpretation of the entered number.
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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