Calculator
Battery Runtime & Capacity Calculator
Calculate energy, runtime, required capacity, charge time and nominal series/parallel values.
Battery Runtime & Capacity Calculator
Calculate energy, runtime, required capacity, charge time and nominal series/parallel values.
Result
Result
3 h 42 min
mAh, Ah and Wh
mAh and Ah describe charge; Wh describes energy. Voltage is required: Wh = Ah × V. Equal mAh at different voltages does not mean equal energy.
Runtime and losses
Runtime is usable Wh ÷ W or usable Ah ÷ A. Usable capacity limits the battery portion; efficiency describes conversion losses.
Required capacity
Load × runtime gives output energy. Dividing by usable fraction and efficiency gives nominal energy and then Ah at the entered voltage.
Charge time
Ah ÷ A or Wh ÷ W is a mathematical estimate. Real chargers vary current and power; no charging curve is simulated.
Series and parallel
For identical units, series raises voltage and parallel raises Ah. This is nominal math, not pack construction, BMS or safety guidance.
Power banks and reality
Power-bank mAh often refers to internal cell voltage. Output voltage, losses, load, age and temperature can change runtime.
Frequently asked questions
How long will a 5000 mAh battery last?
Voltage and load are required; mAh alone does not determine energy.
How do I convert mAh to Wh?
Divide by 1000 and multiply by voltage.
Why is voltage required?
Only Ah × V gives energy in Wh.
How is runtime calculated from watts?
Divide usable Wh by load W.
How is runtime calculated from amps?
Divide usable Ah by load current.
How much capacity do I need?
Calculate load × time and account for factors and voltage.
How long does charging at 2 A take?
Ideally Ah ÷ 2 A; real charging may take longer.
What is 3S4P?
Three identical units in series and four strings in parallel.
Does series double mAh?
No. Series raises voltage.
Does parallel double voltage?
No. Parallel raises Ah.
Why compare Wh?
Wh includes voltage and charge capacity.
Are age and temperature modeled?
No, they are only noted as real-world influences.
Does it calculate a BMS?
No pack or safety design is provided.