Calculate timing, cutoff frequency, and charge curves
Time Constant (τ = RC)
1000.00 ms
Cutoff Frequency
0.16 Hz
Rise Time (10-90%)
2.197 s
Time to 63.2%
999.67 ms
τ × 5 (99.3%)
5.000 s
A resistor is a passive element that limits current, and a capacitor is a passive element that stores charge in an electric field. An RC network is a first-order circuit formed by those two elements, and its transient response is defined by the time constant tau.
In electronics, this response is used for low-pass filtering, delay generation, edge shaping, and reset timing. The same equations are also used to check whether component tolerances could shift a timing threshold outside the allowed design window.
An RC time constant is the product of resistance and capacitance, and it defines how quickly a first-order RC network charges, discharges, or responds to a step input.
For an RC charging curve, the exponential response reaches 63.2 percent of its final value after one time constant.
Designers commonly use five time constants because an RC network reaches about 99.3 percent of its final value by 5 tau.
The -3 dB cutoff frequency of a simple RC low-pass filter is one divided by 2 pi RC.
It is used in debounce circuits, power-on reset timing, analog filtering, sensor conditioning, and delay networks.