RC Time Constant Calculator
τ = R×C for general RC circuit timing.
Capacitance unit
Time constant τ = R × C
1000 ms
1τ
1000 ms
≈ 63.2% settled
2τ
2 s
≈ 86.5% settled
3τ
3 s
≈ 95.0% settled
5τ
5 s
≈ 99.3% settled
RC cutoff frequency fc = 1 / (2πRC)
0.1592 Hz
What is this tool?
In an RC circuit the time constant τ = R×C sets how quickly voltage approaches its final value. About 63% of the change happens in 1τ, ~95% by 3τ, and ~99% by 5τ. This tool focuses on that general analysis (not a capacitor percentage charge UI).
How to use it
- Enter R and C (with unit selectors if provided).
- Read τ and the 1τ / 2τ / 3τ / 5τ times.
- Verify against your schematic and component tolerances.
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