This tool calculates the frequency of a square wave from its period

Enter the value of the period and use the drop down menu to select the units: second, millisecond, microsecond, nanosecond or picosecond.

The output value of frequency is provided in the second row. Default unit is Hz, although the drop down can be used to select Hz, kHz, MHz or GHz.

**Formula**

**F = 1/T**

where,

- T is the period of the square wave
- F is the frequency

**Example Calculation**

A period of 1 µs is equivalent to a frequency of 1 MHz.

**Background**

**The fundamental frequency** of a square wave can be measured by any of the following electronic instruments:

- Frequency Counter
- Oscilloscope
- Spectrum Analyzer

**A frequency counter** will give you the value directly in Hz/kHz/MHz/GHz.

Most **modern digital oscilloscopes** will provide a built-in function that gives this value. In older analog oscilloscopes, the value has to be derived by measuring the period or time interval from one rising edge to the next as shown in the picture below, or from one falling edge to the next.

The frequency is independent of the duty cycle. In other words, it is the same for symmetrical square waves (50% high and 50% low) and also pulses where the On and Off time durations are not the same.

In the case of a **spectrum analyzer**, a square wave presents as a set of repeated spectral lines that are harmonics of frequency spread apart. The square wave harmonics calculator gives the values. The frequency at which the signal is the strongest represents the fundamental frequency of the square wave.