The cut off frequency of a low pass RC filter is given by the formula

Low-Pass RC filter:

• One simple low-pass filter circuit consists of a resistor in series with a load and a capacitor in parallel with the load.
• The capacitor exhibits reactance, and blocks low-frequency signals, forcing them through the load instead.
• At higher frequencies, the reactance drops, and the capacitor effectively functions as a short circuit.

The cut-off frequency is also known as the break frequency, turnover frequency, corner frequency and it is given by

\({f_c} = \frac{1}{{2\pi RC}}\)