Calculate how long it takes to charge a capacitor through a resistor.
RC Circuit Parameters
Calculation Results
Enter circuit values to find charge time
Quick Reference
τ (Tau)R × C (Time Constant)
VsSource Voltage
VcCapacitor Voltage
lnNatural Logarithm
Overview
In an RC circuit, the capacitor voltage rises exponentially toward the source voltage. The speed of this process is governed by the time constant τ = RC.
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Pro Tips
One time constant (1τ) charges a capacitor to ~63.2%.
After five time constants (5τ), it is considered fully charged (~99.3%).
The charging rate slows down as the capacitor voltage approaches the supply voltage.
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Fun Facts
"Camera flashes wait for a capacitor to charge before they can fire again."
"RC circuits are the basis for many simple timers and oscillators."
"Technically, a capacitor never reaches 100% charge in a purely theoretical model, but for all practical purposes, it does."
