Capacitor Discharge Calculator
⚡ Electricity & magnetism. Use the Capacitor discharge formula to find charge left, starting charge, time, time constant rc: pick the value you want, type the others, and the answer updates as you go.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Charge left | C |
| Starting charge | C |
| Time | s |
| Time constant RC | s |
Worked example
Find the charge left when Starting charge = 0.012 C, Time = 1 s, Time constant RC = 1 s.
Using Q = Q0 e^(-t/RC): Charge left = 0.0044146 C.
Frequently asked questions
What is the formula for Capacitor discharge?
Q = Q0 e^(-t/RC).
What do the letters stand for, and what units are used?
Charge left in C, Starting charge in C, Time in s, Time constant RC in s.
How do you calculate charge left?
Put the values into Q = Q0 e^(-t/RC). For example, with Starting charge = 0.012 C, Time = 1 s, Time constant RC = 1 s, charge left = 0.0044146 C.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (charge left, starting charge, time, time constant rc) and fill in the others: it rearranges the formula for you.
