This is simply calculated at how many cycles (waves) occur every second. These cycles are repeated so really we only need to look at how many cycles (waves) occur in one second.
The result is measured as cycles/second and this unit of frequency is called a Hertz and the abbreviation is Hz.
Using the waves/arcs analogy above think of each wave as a cycle and the amount of waves that are dispersed in one second are calculated as frequency. You cannot get simpler than that…..how many cycles hit you in one second.