RC Time Constant Calculator
The RC time constant tells you how fast a capacitor charges or discharges through a resistor, and it is the backbone of timers, filters and debounce circuits. This calculator multiplies your resistance in ohms by your capacitance in farads to give tau, the time constant in seconds. One time constant is the time to reach about 63 percent of the final voltage, and after five time constants the capacitor is considered fully charged or discharged at over 99 percent. The tool also gives you the cutoff frequency of the resulting low pass filter, which is one over two pi R C, so you can see how the same components behave in the frequency domain. Enter your R and C values, choosing convenient units like kilohms and microfarads, and the results update instantly. Everything runs locally in your browser.
How to use RC Time Constant Calculator
- Enter the resistance value in your chosen ohm unit.
- Enter the capacitance value in your chosen farad unit.
- Read tau, the 63 percent charge time.
- Read the 5 tau time for full charge or discharge.
Frequently asked questions
What does the RC time constant tau mean?
Tau is the product of resistance and capacitance and equals the time for a capacitor to charge to about 63 percent of the supply voltage through that resistor.
Why does the tool report a 5 tau time?
A capacitor is considered fully charged or discharged after five time constants, roughly 99 percent, so 5 tau is the practical settling time it reports.
What units go in and out?
Enter resistance in ohms and capacitance in farads, or scaled units like kilohms and microfarads, and the time constant comes back in seconds.
What is RC Time Constant Calculator?
The RC time constant tells you how fast a capacitor charges or discharges through a resistor, and it is the backbone of timers, filters and debounce circuits. This calculator multiplies your resistance in ohms by your capacitance in farads to give tau, the time constant in seconds.
Is RC Time Constant Calculator free to use?
Yes. RC Time Constant Calculator is completely free, with no sign-up and no usage limits.
Does RC Time Constant Calculator work in a web browser?
Yes. RC Time Constant Calculator runs in any modern web browser. There is nothing to download or install.
Is my data private with RC Time Constant Calculator?
Yes. RC Time Constant Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.
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