Free RC Time Constant Calculator
Calculate the RC time constant of a resistor-capacitor circuit: tau = R * C.
Ω
μF
Time Constant (τ)
1.0000 s
Time Constant (ms)1,000.00 ms
Full Charge Time (5τ)5.0000 s
Time Constant (τ) vs Resistance
RC Time Constant
The time constant characterizes how quickly a capacitor charges or discharges through a resistor.
Formula
τ = R * C
After one time constant, the capacitor reaches about 63.2% of its final value. After 5τ, it is over 99% charged.
Example Calculation
A 10 kΩ resistor with a 100 μF capacitor.
- 01τ = R * C
- 02τ = 10000 * 100e-6
- 03τ = 1.0 s
- 045τ = 5.0 s (99.3% charged)
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