Foundations
Charge transferred
- where
- charge (C)
- current (A)
- time (s)
Explain this equation
Works out how much charge a steady current moves in a given time. Useful when relating current draw to battery or capacitor charge.
Q is the charge transferred in coulombs. I is the current in amperes and t is how long it flows, in seconds. Charge is a quantity of electricity, not energy.
Since one ampere is one coulomb per second, multiplying amperes by seconds gives coulombs. It is the same definition as I = Q/t, turned round.
Sense check: 2 A for 60 s moves 120 C. One ampere-hour is 3,600 C, so a 1 Ah cell holds about 3,600 C of usable charge.
Watch out: coulombs are not joules. To get energy you also need the voltage.
A steady flow transfers more charge when it lasts longer. Multiply amperes by seconds to obtain coulombs.
You can rearrange the relationship to t = Q/I. Charge measures the amount transferred; it is not the same quantity as energy.
Enter your values to see the result.
Common mistake
Calling coulombs watts or joules.
Limits
Use steady current, or the average current for the interval.
Sources
The tools calculate the displayed equation. They do not automatically choose cable sizes, approve installations, supply current regulatory tables, certify equipment or replace inspection and testing.