Physics

Capacitor Charge Time Calculator

Find how long a capacitor takes to reach a target voltage.

Resistance (Ω)

Capacitance (µF)

Supply voltage (V)

Target voltage (V)

Calculated Output

Charge time 0.1386

Formula: t = −R·C·ln(1 − V_target/V_supply)

Step-by-Step Breakdown

1. Values used:

2. Resistance = 1,000 Ω

3. Capacitance = 100 µF

4. Supply voltage = 12 V

5. Target voltage = 9 V

7. Charge time = 0.1386

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The math behind it

The capacitor voltage rises as V(t) = V_supply(1 − e^(−t/RC)). Solving for t gives t = −RC·ln(1 − V_target/V_supply).

1 kΩ, 100 µF, 12 V supply to 9 V → about 0.139 s.

Can it ever fully reach the supply?

Only asymptotically — it gets arbitrarily close but never exactly equal.