Capacitor & Resistor (RC Time Constant) Calculator
Physics & EngineeringCalculate the RC time constant of a resistor-capacitor circuit.
RC Time Constant
The RC time constant in seconds, the time for the capacitor to charge to about 63 percent of its final voltage.
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Frequently Asked Questions
What does the RC time constant represent?
The RC time constant represents the time it takes for a charging capacitor to reach approximately 63.2 percent of its final voltage, or for a discharging capacitor to drop to about 36.8 percent of its initial voltage.
How long does it take for a capacitor to fully charge?
A capacitor is commonly considered fully charged after about 5 time constants, at which point it has reached over 99 percent of its final voltage, a useful practical rule for circuit design.
Why does increasing resistance slow down charging?
Higher resistance limits the current flow into the capacitor, which directly increases the time constant and slows the overall charging or discharging process, since time constant is the product of resistance and capacitance.
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