An inductor calculator helps you determine inductive reactance, LC resonant frequency, and RL circuit impedance for electronics design. Whether you are building filters, tuning circuits, or analyzing RL networks, this tool provides instant results with flexible unit selectors for inductance, capacitance, and frequency.
Inductive Reactance Calculator
Enter frequency and inductance to calculate inductive reactance (XL = 2πfL).
Formulas Used
Inductor Formula Reference
| Quantity | Formula | Description |
|---|---|---|
| Inductive Reactance | XL = 2πfL | Opposition to AC by inductor |
| Capacitive Reactance | XC = 1 / (2πfC) | Opposition to AC by capacitor |
| Resonant Frequency | f = 1 / (2π√LC) | LC circuit natural frequency |
| RL Impedance | Z = √(R² + XL²) | Total opposition in RL circuit |
| Phase Angle | θ = arctan(XL / R) | Angle between V and I |
| Time Constant | τ = L / R | RL circuit response time |
How to Use the Inductor Calculator
Inductors are fundamental components in electronics, used in filters, power supplies, RF circuits, and signal processing. This inductor calculator provides three essential calculation modes to help you design and analyze circuits involving inductors. All calculations run instantly in your browser with no signup required.
Mode 1: Inductive Reactance
Select the Reactance mode and enter a frequency and inductance value. The calculator applies the formula XL = 2πfL to determine the inductive reactance in ohms. Use the unit selectors to work in Hz, kHz, or MHz for frequency, and μH, mH, or H for inductance. For example, a 10 mH inductor at 1 kHz produces approximately 62.83 Ω of reactance.
Mode 2: LC Resonant Frequency
Switch to LC Resonance mode and enter both inductance and capacitance. The calculator finds the resonant frequency using f = 1 / (2π√(LC)). At this frequency, the inductive and capacitive reactances are equal and cancel out, creating a resonant peak. This is essential for designing bandpass filters, oscillators, and antenna matching networks. The result also shows the reactance values at resonance.
Mode 3: RL Circuit Impedance
Use RL Circuit mode when you need the total impedance of a series resistor-inductor combination. Enter resistance in ohms, inductance with your preferred unit, and frequency. The calculator computes impedance Z = √(R² + XL²), phase angle, and the RL time constant τ = L/R. The phase angle tells you how far the current lags behind the voltage, which ranges from 0° (purely resistive) to 90° (purely inductive).
Practical Tips
When working with inductor calculations, keep in mind that real inductors have parasitic resistance (DCR) that affects performance at low frequencies, and parasitic capacitance that creates a self-resonant frequency at high frequencies. For precision work, measure your actual inductor values with an LCR meter rather than relying solely on nominal specifications. This calculator provides ideal theoretical results that serve as an excellent starting point for circuit design.
FAQ
Is this inductor calculator completely free?
Yes, this calculator is 100% free with no limits. You can perform as many calculations as you need without creating an account or paying anything.
Is my data safe when using this tool?
Absolutely. All calculations run entirely in your browser using client-side JavaScript. No data is sent to any server, stored, or logged. Your values never leave your device.
What is inductive reactance?
Inductive reactance (XL) is the opposition an inductor presents to alternating current. It increases with frequency and inductance, calculated as XL = 2πfL. Unlike resistance, reactance causes a 90-degree phase shift between voltage and current.
How do I calculate LC resonant frequency?
LC resonant frequency is the frequency at which an inductor and capacitor resonate, calculated as f = 1 / (2π√(LC)). At resonance, inductive and capacitive reactances are equal and cancel each other out, creating maximum energy transfer.
What is the difference between reactance and impedance?
Reactance is the opposition from a single reactive component (inductor or capacitor), while impedance combines both resistance and reactance. For an RL circuit, impedance Z = √(R² + XL²), which is always greater than or equal to either R or XL alone.
What units should I use for inductance?
Inductance is measured in henrys (H). Common sub-units include millihenrys (mH, 10⁻³ H) for power inductors and microhenrys (µH, 10⁻⁶ H) for RF and switching circuits. This calculator supports all three units with automatic conversion.
What is the RL time constant?
The RL time constant (τ = L/R) tells you how quickly current reaches its steady-state value in an RL circuit. After one time constant, current reaches about 63.2% of its final value. After five time constants, it is considered fully established at 99.3%.
Can I use this for RF circuit design?
Yes. The reactance and resonant frequency calculators are particularly useful for RF filter design, impedance matching networks, and tank circuits. Use microhenry (µH) and picofarad (pF) units for typical RF frequency ranges.