Free · Tech and electronics calculators 💻

Battery Watt Hours and C Rate

Nominal energy in Wh is voltage times capacity in Ah. Current in amperes is capacity in Ah times C rate; ideal runtime in minutes is 60 divided by C rate.

  • Formula & worked example
  • Private in your browser
  • No signup
Go to tool

Calculator inputs

Loading calculator…

How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

Worked example: watt hours = 120; discharge current = 5; runtime to full capacity = 120. See the assumptions for units and model limits.

voltage * ampere_hours = watt_hours; ampere_hours * c_rate = discharge_current; runtime_to_full_capacity = 60/c_rate

Worked example

Enter these known values and leave the other values blank.

Voltage
12 V
Battery capacity
10 Ah
C-rate
0.5 C
Stored energy
120 Wh
Discharge current
5 A
Runtime to full capacity
120 min

Assumptions and limitations

  • Nominal energy in Wh is voltage times capacity in Ah. Current in amperes is capacity in Ah times C rate; ideal runtime in minutes is 60 divided by C rate.
  • These are ideal constant-rate relationships. Actual delivered capacity varies with temperature, cutoff, age and load; a positive C rate is required for finite runtime.

Common questions

What does this model assume?

Nominal energy in Wh is voltage times capacity in Ah. Current in amperes is capacity in Ah times C rate; ideal runtime in minutes is 60 divided by C rate.

Can I solve for a different value?

Clear the desired editable unknown and enter sufficient independent known values. Unit selectors preserve quantities; singular or unsupported inverse branches remain incomplete.

References

Reject singular physical denominators and fractional discrete counts using exact isInteger checks.

Explore tech and electronics calculators 💻 or browse all everyday life calculators.