A method for deconvoluting measured mass spectrometry data, the method comprising: receiving measured mass spectrometry data representing at least two molecular moieties each having a respective isotopic pattern, wherein at least two of said isotopic patterns overlap; iteratively filling a set of mass channels to produce an approximated version of the mass spectrometry data, said iterative filling comprising a number of iterations, each iteration comprising filling one or more of the mass channels with a chunk of intensity data according to the isotopic pattern of a respective one of the two or more molecular moieties selected for said iteration; terminating said iterative filling when a fitness criterion is met indicating a fit of the approximated version of the mass spectrometry data to the measured mass spectrometry data; and determining the amount of each molecular moiety that produced the measured mass spectrometry data based on the total amount of fills according to the respective isotopic pattern of said molecular moiety.