# Empirical formula

An **empirical formula** is a mathematical relationship that has been discovered empirically , i.e. using the method of trial and error , or established from experimental data as an approximate formula . As a result, at the time of its discovery, it generally had no theoretical justification from which it could have been deductively derived.

In particular, these are also formulas that have no direct unit relationship between the values to be used and the resulting quantities . In individual cases, therefore, additional instructions for the empirical formulas define the units. This is expressed in the fact that you have to convert the quantities to be used into a certain unit and then only have to enter their numerical values ( numerical value equation ). The resulting numerical value must then be assigned to a unit that does not result from the equation itself and must therefore also be taken from the side remarks.

Such equations are particularly widespread in engineering and hydrology , but also in numerous other natural sciences.

Examples:

- Johannes Kepler found the laws named after him , which describe the observed movements of the planets.
- Johann Jakob Balmer was able to resolve the wave numbers of the lines in the spectrum of hydrogen into whole ratios through skillful reshaping, see Balmer series .
- Mordehai Milgrom's formula describes the spiral motion of galaxies .
- In astronomy, the Titius-Bode series describes a rule of the distances between planets and the sun .
- The Magnus formula is used to determine the approximate saturation vapor pressure of water .
- In chemistry , it is the simplest number ratio in which elements occur in a chemical compound, see ratio formula .
- Formula for calculating the perceived temperature , due among other things to the wind chill effect