Technical Abstract: In biocatalysis research, determination of enzyme kinetics, microbial growth rates, substrate utilization rates, and product accumulation rates sometime require derivatives to be calculated with a method that can be duplicated and yields consistent results. In this paper, several methods that have been suggested in the literature are discussed and the result is presented graphically. A spreadsheet methodology was developed to handle the complicated equations. The results show that a cubic spline method proved more versatile in its use, even though the spreadsheet programming was challenging. The methods discussed were tested with published literature data for cell growth, and a preferred technique was developed based on smoothing the data and using this smooth data for rate calculations.