The operating (or Larmor) frequency  of a magnet (usually quoted as absolute value in MHz) is calculated from the Larmor equation
where  is the induction of the magnet (SI units of Tesla), and  is the magnetogyric ratio of the nucleus  an empirically measured fundamental constant determined by the details of the structure of each nucleus. For example, the proton operating frequency for a 1 Tesla magnet is calculated as:
MRI scanners are often referred to by their field strengths  (e.g. "a 7 T scanner"), whereas NMR spectrometers are commonly referred to by the corresponding proton Larmor frequency (e.g. "a 300 MHz spectrometer", which has a  of 7 T ). While chemical shift is referenced in order that the units are equivalent across different field strengths, the actual frequency separation in Hertz scales with field strength (). As a result, the difference of chemical shift between two signals (ppm) represents a larger number of Hertz on machines that have larger  and therefore the signals are less likely to be overlapping in the resulting spectrum. This increased resolution is a significant advantage for analysis. (Larger field machines are also favoured on account of having intrinsically higher signal arising from the Boltzmann distribution of magnetic spin states.)