# Frequency Aliasing Calculator

If a signal is sampled at a rate that is lower than the Nyquist rate, it will be aliased.

Enter the sampling frequency and the input frequency. The calculator provides the frequency at which the input will appear in the output spectrum.

## Background

In this post we provided a Nyquist frequency calculator. At frequencies above this value, the input signal will be aliased.

As an example, if the sampling frequency is 10 kHz and the input frequency is 7 kHz (higher than the Nyquist frequency of 5 kHz) then it will appear at 3 kHz. This is an example of aliasing.

Now let’s say we had two input signals, one at 7 kHz and the other at 3 kHz, then the aliased 7 kHz signal will overlap with the non-aliased 3 kHz signal and it will erroneously appear that there’s only one input signal.

If we know that signals can be as high as 7 kHz, then the Nyquist rate is calculated to be 14 kHz. This is the minimum frequency that the input signal should be sampled at to prevent aliasing.