Time constant is a measurement of the time needed to charge or discharge a capacitor by ~63.2% of the differenece between the old value and new value after an impulse that induces a change has been applied.
Calculate the energy (E) and time constant (RC) in a capacitor for the given voltage across it. You can determine two different values from the calculator. Time constant (T) can be determined from the values of capacitance (C) and load resistance (R). Energy stored on a capacitor (E) can be determined by giving all three inputs: voltage (V), capacitance and load resistance.
Energy Stored = Voltage2 x Capacitance / 2
Time Constant = Capacitance x Load Resistance