Time constant τ calculation

Online calculator and formulas for calculating the time constant τ (tau) of resistor and capacitor

On this page you can calculate the time constant, resistance or capacitor of a resistor and a capacitor circuit.

Time constant calculator

  What should be calculated?
Time constant
Capacitor
Resistor
 Input
Capacitor
Resistor
Time constant
  Result
Capacitor
Resistor
Time constant
Decimal places

Formula for calculating the time constant

The time constant of an RC element (low pass) is the product of R * C. Its unit of measurement is seconds. The symbol is the Greek letter Τ (tau)

The time constant is required to calculate the state of charge at a specific point in time when charging or discharging the capacitor.

After a period of 3 time constants, the output signal has approx. 95% of the size of the input signal. After 5 Τ the charge is approx. 99.3%.

\(\displaystyle Τ=R ·C\)         \(\displaystyle R=\frac{Τ}{C}\)         \(\displaystyle C=\frac{Τ}{R}\)

Legend

\(\displaystyle R\)

Resistor

\(\displaystyle C\)

Capacitor

Τ

Time constants

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