RC Circuit Time Constant Calculator

Calculate the time constant (τ = RC), voltage, and current at any time for an RC circuit during charging or discharging.

Resistance

Capacitance

Initial / Supply Voltage

Time

Tab to move between fields

Time Constant (τ)

0 s

Discharge Voltage at t

1.84 V

Charging Voltage at t3.16 V

Current at t0 A

Time to 37% (1τ)0 s

Time to 1% (4.6τ)0 s

How to Use This Calculator

Enter Resistance, Capacitance, and Initial / Supply Voltage.
Set Time.
Review Time Constant (τ) and Discharge Voltage at t.
Use Charging Voltage at t and Current at t (A) to inform your decision.
Use the chart to visualize the results and explore different scenarios by adjusting inputs.

How the result changes with Resistance

Resistance: Resistance in ohms.
Capacitance: Capacitance in farads. 1 μF = 0.000001 F, 1 nF = 1e-9 F.
Initial / Supply Voltage: Initial voltage across the capacitor (discharge) or supply voltage (charge).
Time: Time at which to evaluate the circuit state.

Identify Input Parameters
4 parameters
Resistance = 1000, Capacitance = 0.000001, Initial / Supply Voltage = 5, Time = 0.001 = 4 input(s) provided
Calculate Time Constant
Time Constant
0.001 = 0.001
Calculate Discharge Voltage at t
Discharge Voltage at t
1.8394 = 1.8394
Calculate Charging Voltage at t
Charging Voltage at t
3.1606 = 3.1606
Calculate Current at t
Current at t
0.0018394 = 0.0018394