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RLC Circuit Calculator

Step and sinusoidal response of series RLC circuits: natural frequency, damping ratio, Q factor, and bandwidth

Reviewed by Christopher FloiedPublished Updated

This free online rlc circuit calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Supports both metric (SI) and imperial units with built-in unit selection dropdowns on every input field, so you can work in whatever units your problem provides. Designed for engineering students and professionals working through coursework, design projects, or quick reference calculations.

RLC Circuit Calculator

Step or sinusoidal response, natural frequency, damping, and quality factor for series RLC.

Natural Freq. ωn

447.21 rad/s

Resonant Freq. f₀

71.18 Hz

Damping Ratio ζ

0.2236

Classification

Underdamped

Quality Factor Q

2.236

Bandwidth BW

31.83 Hz

Time Constant τ

10.00 ms

Step Response v_C(t)

Transient Response Data Table

t (ms)v_C (V)
0.0000.000000
0.5000.024090
1.0000.092120
1.5000.196700
2.0000.329400
2.5000.481240
3.0000.643210
3.5000.806670
4.0000.963740
4.5001.107580
5.0001.232630
5.5001.334760
6.0001.411310
6.5001.461090
7.0001.484280
7.5001.482320
8.0001.457690
8.5001.413710
9.0001.354320
9.5001.283790
10.0001.206530
10.5001.126830
11.0001.048710
11.5000.975710
12.0000.910810
12.5000.856320
13.0000.813810
13.5000.784180
14.0000.767590
14.5000.763590
15.0000.771170
15.5000.788880
16.0000.814900
16.5000.847220
17.0000.883700
17.5000.922220
18.0000.960760
18.5000.997490
19.0001.030850
19.5001.059570
20.0001.082730
20.5001.099770
21.0001.110460
21.5001.114900
22.0001.113470
22.5001.106800
23.0001.095710
23.5001.081130
24.0001.064100
24.5001.045650
25.0001.026800
25.5001.008470
26.0000.991480
26.5000.976510
27.0000.964080
27.5000.954540
28.0000.948050
28.5000.944650
29.0000.944190
29.5000.946420
30.0000.950980
30.5000.957420
31.0000.965270
31.5000.974020
32.0000.983170
32.5000.992240
33.0001.000820
33.5001.008540
34.0001.015130
34.5001.020370
35.0001.024140
35.5001.026420
36.0001.027220
36.5001.026660
37.0001.024890
37.5001.022110
38.0001.018540
38.5001.014440
39.0001.010040
39.5001.005580
40.0001.001290
40.5000.997340
41.0000.993900
41.5000.991070
42.0000.988930
42.5000.987520
43.0000.986840
43.5000.986840
44.0000.987470
44.5000.988630
45.0000.990220
45.5000.992130
46.0000.994220
46.5000.996390
47.0000.998520
47.5001.000520
48.0001.002310
48.5001.003810
49.0001.005000
49.5001.005830
50.0001.006310
50.5001.006440
51.0001.006250
51.5001.005790
52.0001.005100
52.5001.004230
53.0001.003240
53.5001.002190
54.0001.001140
54.5001.000140
55.0000.999220
55.5000.998430
56.0000.997790
56.5000.997310
57.0000.997010
57.5000.996880
58.0000.996900
58.5000.997070
59.0000.997370
59.5000.997760
60.0000.998220
60.5000.998720
61.0000.999230
61.5000.999730
62.0001.000200
62.5001.000610
63.0001.000960
63.5001.001220
64.0001.001400
64.5001.001500
65.0001.001520
65.5001.001470
66.0001.001350
66.5001.001170
67.0001.000960
67.5001.000730
68.0001.000480
68.5001.000230
69.0000.999990
69.5000.999780
70.0000.999600
70.5000.999450
71.0000.999350
71.5000.999280
72.0000.999260
72.5000.999270
73.0000.999320
73.5000.999390
74.0000.999490
74.5000.999600
75.0000.999720
75.5000.999840
76.0000.999960
76.5001.000060
77.0001.000160
77.5001.000240
78.0001.000300
78.5001.000340
79.0001.000360
79.5001.000360
80.0001.000340
80.5001.000310
81.0001.000270
81.5001.000220
82.0001.000160
82.5001.000100
83.0001.000040
83.5000.999990
84.0000.999940
84.5000.999900
85.0000.999870
85.5000.999840
86.0000.999830
86.5000.999820
87.0000.999830
87.5000.999840
88.0000.999860
88.5000.999880
89.0000.999910
89.5000.999940
90.0000.999970
90.5000.999990
91.0001.000020
91.5001.000040
92.0001.000060
92.5001.000070
93.0001.000080
93.5001.000080
94.0001.000080
94.5001.000080
95.0001.000070
95.5001.000060
96.0001.000050
96.5001.000040
97.0001.000020
97.5001.000010
98.0001.000000
98.5000.999980
99.0000.999970
99.5000.999970
100.0000.999960

Formulas

ωn = 1/√(LC) = 447.21 rad/s
ζ = R/(2√(L/C)) = 0.2236
Q = (1/R)√(L/C) = 2.236
BW = R/L = 200.00 rad/s

How to Use This Calculator

1

Enter your input values

Fill in all required input fields for the RLC Circuit Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.

2

Review your inputs

Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.

3

Read the results

The RLC Circuit Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.

4

Explore parameter sensitivity

Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.

Formula Reference

RLC Circuit Calculator Formula

See calculator inputs for the governing equation

Variables: All variables and their units are labeled in the calculator interface above. Input fields accept values in multiple unit systems — select your preferred unit from the dropdown next to each field.

When to Use This Calculator

  • Use the RLC Circuit Calculator when solving homework or exam problems that require quick numerical verification of your hand calculations — instant feedback helps identify arithmetic errors before they propagate.
  • Use it during the early design phase to rapidly iterate on parameters and narrow down feasible configurations before committing time to detailed finite element simulations or full design packages.
  • Use it when reviewing a colleague's calculation or checking a vendor's data sheet for plausibility — a quick sanity check can prevent costly downstream errors.
  • Use it to generate reference data for a technical report or presentation without manual computation, ensuring consistent, reproducible numbers throughout the document.
  • Use it in the field when a quick estimate is needed and a full engineering software package is not available.

About This Calculator

The RLC Circuit Calculator is a precision engineering calculation tool designed for students, engineers, and technical professionals. Step and sinusoidal response of series RLC circuits: natural frequency, damping ratio, Q factor, and bandwidth All calculations are performed using established engineering formulas from the relevant scientific literature and standards. Inputs support both metric (SI) and imperial unit systems, with unit conversion handled automatically — simply select your preferred unit from the dropdown next to each field. Results are computed instantly in the browser without sending data to a server, ensuring both speed and privacy. This calculator is intended as a supplementary tool for learning and design exploration; always verify results against authoritative references for safety-critical applications.

The Theory Behind It

A series RLC circuit contains a resistor, inductor, and capacitor in series, driven by a voltage source. Its natural behavior is determined by the damping ratio ζ and natural frequency ω_n, analogous to a mechanical spring-mass-damper system. Natural frequency ω_n = 1/√(LC). Damping factor α = R/(2L). Damping ratio ζ = α/ω_n = (R/2)·√(C/L). Three damping regimes: underdamped (ζ < 1, oscillatory response, most common), critically damped (ζ = 1, fastest non-oscillatory response), overdamped (ζ > 1, slow non-oscillatory return). For underdamped series RLC, the damped oscillation frequency is ω_d = ω_n·√(1−ζ²). Step response: oscillatory ring-down about final value for underdamped; exponential approach for critical and overdamped. Sinusoidal (steady-state) response: peak amplitude at resonance (ω = ω_n) for underdamped, lower and broader peak for higher damping. RLC circuits are the electrical equivalent of mechanical vibration systems, and the same math applies to both. They are used in signal filters, oscillators, antenna matching networks, and power conditioning. The calculator analyzes both transient (step) and steady-state (sinusoidal) response of series RLC circuits.

Real-World Applications

  • Tuned radio receivers: RLC tank circuits select specific radio frequencies from the broad spectrum picked up by the antenna.
  • Band-pass and band-stop filters: allow or block specific frequency ranges in audio and communication circuits.
  • Voltage regulator smoothing: RLC filtering reduces ripple in DC power supplies after rectification.
  • Crystal radio design: classical wireless radio uses a simple LC tank for tuning without amplification.
  • Transient voltage suppression: RLC circuits absorb voltage spikes and protect sensitive electronics.

Frequently Asked Questions

What is an RLC circuit?

An electrical circuit containing resistance R, inductance L, and capacitance C. These three elements represent dissipation, magnetic energy storage, and electric energy storage respectively. Series and parallel RLC circuits have different response characteristics but are both governed by the same ω_n, ζ, and damping regime concepts as mechanical oscillators.

What's the resonant frequency of an RLC circuit?

ω_r = 1/√(LC), or f_r = 1/(2π√(LC)) in Hz. At this frequency, inductive and capacitive reactances cancel, leaving only resistance. For L = 10 mH and C = 10 μF: f_r = 1/(2π·√(0.01·0.00001)) = 1/(2π·0.0003162) ≈ 503 Hz. At resonance, the circuit has minimum impedance (series) or maximum impedance (parallel).

What's Q for an RLC circuit?

For series RLC: Q = (1/R)·√(L/C) = ω_r·L/R. For parallel RLC: Q = R·√(C/L) = R/(ω_r·L). Q is the ratio of stored to dissipated energy per cycle, measuring how sharply tuned the circuit is. High Q (> 10) gives sharp frequency selectivity; low Q (< 1) gives broad response. Q also relates to the damping ratio: ζ = 1/(2Q).

When does an RLC circuit oscillate?

When underdamped (ζ < 1, equivalent to Q > 0.5). The natural frequency of oscillation is ω_d = ω_n·√(1−ζ²), slightly lower than ω_n. Overdamped circuits (ζ > 1) return to equilibrium without oscillation. Critically damped (ζ = 1) is the fastest non-oscillating response. Most filter designs are underdamped to provide frequency selectivity.

What's the step response of an underdamped RLC?

Oscillating decay about the steady-state value: v(t) = V_ss·(1 − e^(−αt)·(cos(ω_d·t) + (α/ω_d)·sin(ω_d·t))), where V_ss is the final voltage, α = R/(2L), and ω_d = √(ω_n² − α²). The oscillation period is 2π/ω_d, and the amplitude decays exponentially with time constant 1/α. Higher R (or lower L) means faster decay and less ringing.

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References & Further Reading