AC Voltage Divider Calculator

Analyze divider behavior across resistive and reactive networks. Compare RMS and peak outputs with ease. Export results to CSV, then print clean PDFs today.

Inputs
Enter Source, Frequency, and Impedances
The result appears above this form after submission.
V
Use RMS or Peak mode below.
deg
Phase reference for phasor calculations.
Results include both RMS and peak.
ω = 2πf is used in reactance.
Impedance Z1 (Series / Top Element)
Choose a model, then enter values.
Used by R, RL, RC, RLC types.
Used by L, RL, RLC types.
Used by C, RC, RLC types.
Ω
Used only by Custom type.
Ω
Positive Im is inductive; negative is capacitive.
Impedance Z2 (Bottom Element / Across Output)
Choose a model, then enter values.
Used by R, RL, RC, RLC types.
Used by L, RL, RLC types.
Used by C, RC, RLC types.
Ω
Used only by Custom type.
Ω
Positive Im is inductive; negative is capacitive.
Optional Load in Parallel with Z2
Z2eff = Z2 ∥ ZL when enabled.
Load Impedance ZL (Parallel Load)
Choose a model, then enter values.
Used by R, RL, RC, RLC types.
Used by L, RL, RLC types.
Used by C, RC, RLC types.
Ω
Used only by Custom type.
Ω
Positive Im is inductive; negative is capacitive.
Formula Used
AC Divider with Complex Impedances

An AC divider uses complex impedance so phase and magnitude are preserved. For two series impedances, the output is taken across Z2.

This calculator reports magnitude and phase in degrees, plus RMS and peak voltage values for convenience.

How to Use
Step-by-Step
  1. Enter the input voltage magnitude and phase.
  2. Select RMS or peak mode for the entered magnitude.
  3. Enter frequency and choose the correct unit.
  4. Choose a type for Z1 and provide its R, L, and C values.
  5. Choose a type for Z2 and provide its values.
  6. Optionally enable a parallel load ZL for realistic loading.
  7. Press Calculate to view results above the form.
  8. Use Download CSV or Download PDF for reports.
Example Data
Sample Inputs and Outputs
Case Vin f Z1 Z2 Approx Vout (mag ∠ phase)
Resistive split 10 Vrms ∠0° 1 kHz R = 1 kΩ R = 1 kΩ 5.000 Vrms ∠ 0.000°
RC low-pass output 10 Vrms ∠0° 1 kHz R = 1 kΩ C = 0.1 µF 8.467 Vrms ∠ −32.142°
Inductive divider 120 Vrms ∠0° 60 Hz R = 100 Ω L = 200 mH 72.244 Vrms ∠ 52.984°

Example outputs are rounded. Your results may differ slightly with unit choices and rounding.

Article
Understanding the AC Voltage Divider

1) What an AC Voltage Divider Measures

An AC voltage divider predicts the output phasor across a chosen impedance when a sinusoidal source drives a series network. Unlike a DC split, the output can lead or lag the input. This calculator reports magnitude, phase angle, and gain so you can compare designs quickly.

2) Why Complex Impedance Matters

Resistors keep voltage and current in phase, but inductors and capacitors store energy and shift phase. Complex impedance represents that behavior as Z = R + jX. Using complex arithmetic preserves both amplitude and timing, which is essential for filters, sensor interfaces, and AC measurement circuits.

3) Reactance vs Frequency: Quick Benchmarks

Frequency strongly changes reactance. For a capacitor, Xc = 1/(ωC). At 1 kHz with 0.1 µF, Xc ≈ 1591.55 Ω. For an inductor, Xl = ωL. At 1 kHz with 10 mH, Xl ≈ 62.83 Ω.

4) Interpreting Magnitude, Phase, and dB Gain

The divider ratio Vout/Vin is complex. Its magnitude tells how much the signal is attenuated or amplified by the network, while its angle is the phase shift in degrees. The calculator also shows gain in dB using 20·log10(|Vout/Vin|).

5) Effect of Loading: Z2 in Parallel

Real outputs feed a load, which often reduces the output voltage. When you enable a load impedance, the calculator forms Z2eff = Z2 ∥ ZL. As |ZL| drops, Z2eff usually drops too, lowering |Vout| and changing phase.

6) RMS and Peak Reporting for Real Signals

Many instruments and power calculations use RMS values, while datasheets often quote peak limits. Enter your source as RMS or peak, and the calculator provides both RMS and peak outputs. For a pure sine wave, Vpeak = Vrms·√2, keeping conversions consistent.

7) Power and Reactive Power at the Output

When reactive components exist, power is not only watts. The tool computes complex power for the effective bottom impedance using RMS phasors. The real part is active power P (W). The imaginary part is reactive power Q (var), indicating net inductive (positive) or capacitive (negative) behavior.

8) Engineering Use Cases and Practical Tips

Use this divider model to size RC low‑pass outputs, compensate sensor phase, or estimate attenuation before an ADC. Keep units consistent, verify frequency range, and add a realistic load. If gain changes sharply with frequency, sweep multiple frequencies and export CSV results for comparison.

FAQs
Common Questions

1) Can I use this for purely resistive dividers?

Yes. Choose Resistor (R) for both Z1 and Z2. The phase shift will be near 0° and the output magnitude matches the familiar DC ratio.

2) What does a negative phase angle mean?

A negative phase indicates the output lags the input reference. This is common when the effective output impedance is more capacitive at the selected frequency.

3) Why does enabling a load change my result?

The load forms a parallel combination with Z2, reducing or reshaping the effective impedance. That changes both the divider ratio magnitude and its phase.

4) Should I enter peak or RMS input voltage?

Either is fine. Select the correct mode and enter the matching magnitude. The calculator then reports both RMS and peak values for Vin and Vout.

5) How accurate are the dB values?

They are computed directly from the complex ratio using 20·log10(|Vout/Vin|). Accuracy depends on your component values and frequency.

6) What if my capacitor value is zero?

For capacitor-based types, a zero or extremely small capacitance makes impedance approach infinity and can create invalid results. Enter a realistic nonzero value for C.

7) Can I model a measured impedance directly?

Yes. Use the Custom (Re + jIm) option and enter the real and imaginary parts in ohms. This is useful when you have impedance analyzer data.