Where A₀ is the initial concentration of reactant (mol L^-1), t is time (s), and k is rate constant (L mol^-1 s^-1). Taking the inverse of each side of this equation gives

Where k is the slope, and 1/A₀ is the intercept, of the best fit line.

To calculate the rate constant enter data pairs (t, A), and then click the Plot tab. To see the rate constant (slope) click the Least-Squares Analysis tab. To pick off a value on the graph, move your cursor to the desired location then click and hold.