Electronic Components
Capacitor Discharging Calculator
Calculate capacitor voltage during RC discharge. The default values illustrate the workflow; replace them with measurements or ratings from one documented condition.
Inputs for this calculation
Enter ratings or measurements that describe one scenario.
How the result is calculated
Start with the equation V = V₀e^(−t/RC). The participating entries are Initial voltage, Resistance, Capacitance, and Elapsed time.
For the example shown, remaining voltage equals 4.415 V. Treat that value as a demonstration, not a recommendation.
Calculate capacitor voltage during RC discharge. If you also need capacitor voltage, continue with Capacitor Charging Calculator.
Reading Remaining voltage
Read Remaining voltage as the outcome of this equation, not as automatic equipment approval. Compare it with voltage rating, current rating, dissipation, tolerance, and transient stress.
Keep the input set beside the output so another reader can reproduce it.
Values this page needs
Record tolerance, bias point, duty cycle, and junction temperature. Do not combine a worst-case value with unrelated nominal data.
Values used below a division bar must stay positive. Check every prefix before entry; micro, milli, kilo, and mega are not interchangeable.
- Initial voltage
- Default example: 12 V. Enter initial voltage in V.
- Resistance
- Default example: 10000 Ω. Enter resistance in Ω.
- Capacitance
- Default example: 100 µF. Enter capacitance in µF.
- Elapsed time
- Default example: 1 s. Enter elapsed time in s.
What the formula leaves out
Additional load current and capacitor leakage shorten the actual discharge time.
The arithmetic intentionally leaves out pulse ratings, frequency behavior, package temperature, and layout. Resolve material omissions before selecting a standard size or rating.
Record tolerance, bias point, duty cycle, and junction temperature.
Keep a reproducible record
Save initial voltage, resistance, capacitance, and elapsed time with remaining voltage. Add the date and any unit conversion.
Transfer remaining voltage without rounding when it becomes another input. Do not round between dependent calculations.
Common questions before using the result
Why does Remaining voltage show several decimals?
Retain the raw result for comparison and create a separately rounded reporting value if needed.
Which input can create an undefined result?
A zero denominator is undefined, so the affected field has a positive minimum.
Which source values should I use for Remaining voltage?
Choose entries that describe the same case. Use data-sheet values at the intended voltage, current, frequency, and temperature.
What should I verify beyond the displayed inputs?
Additional load current and capacitor leakage shorten the actual discharge time. Also consider parasitics, layout inductance, tolerance stack-up, switching edges, and thermal resistance.
What explains a gap between calculated and observed remaining voltage?
First confirm that the measurements match the equation. Then review bias dependence, ESR, leakage, saturation, and self-heating.