Calculate RC oscillator frequency for a Wien bridge or RC phase-shift oscillator, or a 555 astable, or find the R or C needed for a target frequency.

Component scenarios (blank =0%)
For matched networks, all resistors scale together. Independent mismatch is not modeled.

All capacitors scale together; scenarios are not a guaranteed real-circuit tolerance.

Oscillator Frequency Formula

The following nominal formula applies to three identical unbuffered high-pass CR sections (series capacitors and shunt resistors) driven by an inverting amplifier. It is not a universal RC-oscillator or arbitrary-stage formula. Equal-element Wien uses f =1/(2Ï€RC); the ordinary 555 astable uses f =1/[ln(2)(RA+2RB)C].

f = 1 / [2 × pi × R × C × Sqrt(6)]
  • Where f is the frequency (hertz)
  • R is the feedback resistance (ohms)
  • C is the feedback capacitance (farads)
  • This phase-shift model has exactly three equal CR sections; arbitrary stage counts are not supported

Oscillator Frequency Definition

What is an oscillator frequency? An oscillator frequency is typically used to describe the frequency in hertz that an RC or RLC oscillator resonates at.

Example Problem

How to calculate an oscillator frequency?

  1. First, determine the feedback resistance.

    For this example, we are looking at a simple RC oscillator with a feedback resistance of 20 ohms.

  2. Next, determine the feedback capacitance.

    The feedback capacitance of the same oscillator is found to be 35 farads.

  3. Confirm the high-pass network topology.

    This mathematical example uses three identical unbuffered high-pass CR sections and an inverting amplifier; its component values are not a practical design recommendation.

  4. Finally, calculate the frequency.

    Using the formula above, the oscillator frequency is calculated as follows:
    1/ [2*3.14159*20*35*SQRT(2*3) ] = 0.0000928210 hertz.

Oscillator Frequency (RC) Calculator screenshot