Gas fraction estimation is the use of formulae (models) to estimate the gas (gas fraction) or kinds of gas in, for example, a galaxy. Such a method may be used with survey data to perform such estimates on a large number of bodies using available data. Example (using Sloan Digital Sky Survey data):
log10(GHI/S) = - 1.73238(g - r) + 0.215182μi - 4.08451
Methods are devised for different redshifts, in particular to identify star formation potential.