Femtohertz (fHz): SI Unit for Extremely Low Frequencies
The femtohertz (symbol: fHz) is an SI-derived unit of frequency equal to 10−15 hertz. It combines the SI prefix femto-, meaning one quadrillionth, with the hertz, the SI derived unit of frequency. The femtohertz provides a standardized way to represent extremely low frequencies using SI notation.
What Is a Femtohertz?
A femtohertz is a unit of frequency equal to 10−15 hertz. This means one cycle occurs over an extraordinarily long period, making the unit suitable for describing very slow periodic events.
Femtohertz belongs to the International System of Units (SI) and is one-thousandth of a picohertz or one thousand attohertz. It is useful when conventional units such as hertz or millihertz would require extremely small decimal values.
History of the Femtohertz
The femto- prefix was officially adopted by the International Bureau of Weights and Measures (BIPM) in 1964 to represent a factor of 10−15. Combined with the hertz, it forms the femtohertz, extending the SI system to describe exceptionally small frequency values.
Current Uses of the Femtohertz
Femtohertz is primarily used in theoretical physics, cosmology, astronomy, geophysics, and precision scientific research involving extremely slow oscillations or periodic processes. Although rarely encountered in engineering, it provides a standardized SI unit for very low frequencies.
Femtohertz Conversion
One femtohertz is equal to:
- 1 × 10−15 hertz (Hz)
- 0.001 picohertz (pHz)
- 1,000 attohertz (aHz)
- 0.000001 nanohertz (nHz)
You can use ChangeUnit to convert femtohertz to hertz, picohertz, attohertz, and many other frequency units.