Calculate RC time constants, RL time constants, resonant frequency, impedance, reactance and more using this free online electronics calculator.
The Write2Text RC, RL and RLC Circuit Calculator is a free online electronics tool designed for students, hobbyists, technicians, and professional engineers. It helps calculate important electrical characteristics of resistor, capacitor, and inductor circuits without requiring complicated formulas or manual calculations. Simply enter the component values and the calculator instantly computes time constants, resonant frequency, reactance, impedance, phase angle, quality factor, and cut-off frequencies.
Whether you are designing analog filters, studying electronics, repairing equipment, or learning electrical engineering, this calculator provides quick and accurate results directly in your browser.
An RC circuit consists of a resistor (R) and a capacitor (C). These circuits are widely used in timing circuits, filters, oscillators, pulse generators, and power supply smoothing. One of the most important characteristics of an RC circuit is the time constant (τ), which determines how quickly a capacitor charges or discharges.
Formula:
τ = R × C
After one time constant, the capacitor reaches approximately 63.2% of its final voltage. After five time constants, the capacitor is considered fully charged or discharged.
An RL circuit consists of a resistor and an inductor. These circuits are commonly used in power electronics, relay drivers, motor control systems, and filter networks. Unlike capacitors, inductors resist changes in current. The RL time constant determines how quickly current rises or falls in the circuit.
Formula:
τ = L / R
A larger inductance produces a slower current change, while a larger resistance causes the current to stabilize more quickly.
An RLC circuit combines a resistor, capacitor, and inductor. These circuits are widely used in radio receivers, transmitters, oscillators, filters, antenna tuning, and many electronic communication systems.
At the resonant frequency, the inductive reactance and capacitive reactance become equal, causing the circuit to resonate. Resonance allows maximum energy transfer and is one of the most important concepts in electrical engineering.
Unlike ordinary resistance, reactance changes with frequency.
Inductive Reactance
XL = 2πfL
As frequency increases, inductive reactance also increases.
Capacitive Reactance
XC = 1 / (2πfC)
As frequency increases, capacitive reactance decreases.
Impedance is the total opposition to alternating current. It combines resistance and reactance into a single value measured in ohms.
The calculator automatically computes impedance whenever enough information is available, allowing you to analyze AC circuits more effectively.
The phase angle describes the relationship between voltage and current in an AC circuit. A positive phase angle indicates an inductive circuit, while a negative phase angle indicates a capacitive circuit.
Knowing the phase angle is useful when designing filters, power supplies, and communication equipment.
The Quality Factor measures how selective or efficient a resonant circuit is. High-Q circuits have narrow bandwidths and are commonly used in radio frequency applications, while low-Q circuits have wider bandwidths and are often used in filters.
Yes. The RC, RL and RLC Circuit Calculator is completely free to use.
Yes. Values such as 1e-6 or 4.7e-9 can be entered directly.
The calculator supports Ohms, kilo-ohms, mega-ohms, picofarads, nanofarads, microfarads, millifarads, microhenrys, millihenrys and henrys.
Yes. The calculator is fully responsive and works on desktops, tablets, and smartphones.
It is suitable for students, teachers, electronics hobbyists, repair technicians, electrical engineers, and anyone working with RC, RL or RLC circuits.