Formula
This calculator uses the standard rc time constant calculator formula:
Frequently Asked Questions
The RC time constant (τ) is the time it takes for a capacitor to charge to approximately 63.2% of the supply voltage through a resistor. It equals R × C in seconds.
After 5τ (five time constants), the capacitor is considered fully charged to 99.3% of the supply voltage.
τ = R × C, where R is resistance in ohms and C is capacitance in farads. τ is in seconds.
fc = 1 / (2π × R × C). This is the −3 dB frequency where the filter attenuates the signal to 70.7% of its input amplitude.
A low-pass RC filter passes low-frequency signals and attenuates high-frequency signals above the cutoff frequency fc = 1/(2πRC).
A larger capacitor takes longer to charge. Doubling the capacitance doubles the time constant τ and thus doubles the charge time.