Time Constant Calculator

Time Constant Formula:

τ = R × C Charging: V(t) = V_in × (1 - e^-t/τ) Discharging: V(t) = V₀ × e^-t/τ

R = 10 kΩ

R = 100 kΩ

C = 1 μF

C = 10 μF

Input Voltage (V_in):

Resistance (R):

Capacitance (C):

Time (t) for Voltage Calculation (optional):

Enter resistance and capacitance values and click Calculate.

Note: The circuit diagram updates automatically as you enter values.

Auto-calculate as you type

Standard Resistor Finder

Find Standard Resistors for Your Time Constant

Resistance (R):

Desired Time Constant (τ):

Enter resistance or time constant to find standard resistors.

R	Calculated C	Actual Time Constant (τ)	Error (%)

Standard Capacitor Finder

Find Standard Capacitors for Your Time Constant

Capacitance (C):

Desired Time Constant (τ):

Enter capacitance or time constant to find standard capacitors.

C	Calculated R	Actual Time Constant (τ)	Error (%)

RC Circuit Analysis

Charging

V(t) = Vin(1-e^-t/τ)

Discharging

V(t) = V₀e^-t/τ

Comparison

Both curves

Circuit Parameters

Input Voltage (V_in):

Resistance (R):

Capacitance (C):

Analysis Options

Analysis Duration:

Show Time Constants

Show Percentages

Voltage vs Time

Current vs Time

RC Waveform Generator

Input Waveform

Square

Triangle

Sawtooth

Pulse

Amplitude:

Frequency:

Duty Cycle (%):

RC Circuit

Resistance (R):

Capacitance (C):

Analysis Settings

Number of Cycles:

Resolution:

Time Constant Examples & Applications

Basic RC Charging

Given: R = 10 kΩ, C = 1 μF, V_in = 5 V

Time constant τ = 10 × 1 = 10 ms
Voltage at t = 5 ms: V = 5 × (1 - e^-5/10) ≈ 1.97 V
Used in timing circuits and filters

RC Discharging Circuit

Given: R = 47 kΩ, C = 2.2 μF, V₀ = 12 V

Time constant τ = 47 × 2.2 = 103.4 ms
Voltage at t = 100 ms: V = 12 × e^-100/103.4) ≈ 4.53 V
Used in timing delays and power-down circuits

RC Waveform Shaping

Given: R = 1 kΩ, C = 100 nF, f = 10 kHz square wave

Time constant τ = 1 × 0.1 = 0.1 ms
Period T = 100 μs, τ/T = 1:1 ratio
Creates exponential charging/discharging waveforms
Used in pulse shaping and signal conditioning

Time Constant Calculator