About the RC Time Constant Calculator
RC time constant, charge and discharge times, and the filter cut-off frequency.
Also known as: rc circuit calculator, tau calculator, capacitor charge time, rc filter cutoff.
How to use this calculator
- Enter resistance, capacitance, supply voltage.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
τ = R × C · V(t) = V₀(1 − e^(−t/τ)) · f_c = 1 / 2πRC
Worked example
Using the values pre-filled in the calculator above:
- Resistance = 10,000 Ω
- Capacitance = 100 µF
- Supply voltage = 5 V
the calculator returns:
- Time constant τ: 1 s
- In milliseconds: 1,000
- Time to 63% charge: 1 s
- Time to 99% (5τ): 5 s