⏱️ Capacitor Charge Time Calculator
Calculate how long it takes for a capacitor in an RC circuit to charge to a chosen percentage of the supply voltage.
What this calculates
When a capacitor charges through a resistor from a DC source, it doesn’t charge instantly — it follows an exponential curve described by the RC time constant. This calculator finds how long it takes to reach a target percentage of full charge.
The formula
The RC time constant is τ = R × C. The voltage across the capacitor over time follows Vc(t) = V0(1 – e^(-t/τ)), so the time to reach a fraction f of full charge is t = -τ × ln(1 – f). After one time constant, a capacitor reaches about 63% charge; after five time constants, it’s considered essentially fully charged (99.3%).
This calculator is for general electronics education and design reference.