Capacitor Charging
Circuit values
Set the source, R, C and the time t you want to evaluate.
State at time t
Charging curve
How to use this calculator
Set the source voltage, the series resistance, the capacitance and the elapsed time t. The calculator uses V(t) = V₀(1 − e^(−t/τ)) with τ = RC to give the capacitor voltage, the instantaneous current I(t) = (V₀/R)·e^(−t/τ), the stored charge Q = C·V and the percentage charged, all updating in real time. The curve plots the whole charging exponential (0 → 5τ) with a marker at your chosen t, so you can see exactly where on the curve the capacitor sits.
What the value means in a circuit
When a capacitor is connected to a source through a resistor, it doesn't jump to full voltage instantly — it charges exponentially, fast at first (maximum current) and then leveling off as the capacitor voltage approaches the source and the current falls to zero. That behaviour underpins power-on reset, signal coupling, smoothing and timing: after about 5τ the capacitor is, for all practical purposes, fully charged. Knowing V(t) and I(t) at any moment lets you size the resistor, predict inrush current, and determine how long a circuit needs before it reaches its steady state.