Calculate the time it takes to charge a capacitor to the level of the input voltage.

**Formula**

**Vc = Vi (1-e ^{-t/τ})**

where,

**Vi**= Input Voltage**τ**= time constant**Vc**= voltage at the capacitor at time**t**

time constant **τ = RC**, where **R** is resistance and **C** is capacitance.

At **t = 5*RC** = **5τ** (or 5 time constants),

**Vc/ Vi = (1-e^{-5})**

**= 0.9933**

In other words, at **t = 5τ**, the capacitor voltage reaches **99.33%** of the input voltage.

**Example Calculation**

For **R = 1 kΩ** and **C = 1 nF**, the capacitor charging time is **5 µs**.

**Related Calculators**

Capacitor Discharge Time – How long does it take for a cap to discharge to a final voltage level?