# Time constant τ calculation

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

### Description

On this page you can calculate the time constant of a resistor and a capacitor.

The time constant of an RC element (low pass) is the product of R * C. Your unit of measure is the second. The formula 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 the capacitor is being charged or discharged.

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

### Online calculator

#### Enter the two values in the appropriate fields.

Note the unit of measurement

Capacitor

Resistor

Time constant

Decimal places

#### Formula for calculating the time constant

$$\displaystyle τ=R ·C$$

#### Legend

 $$\displaystyle R$$ Resistor $$\displaystyle C$$ Capacitor $$\displaystyle τ$$ Time constants