Reaction end point is characterized by initiating a chemical reaction, obtaining at least three measurements at three different time point of a value associated with an observable indicator of progress of the reaction, and determining an end point value for the indicator from the measurements. An independent claim is also included for a system for characterizing a reaction end point, comprising stored programming capable of inputting at least three measurements, at three different time points, of a value associated with an observable indicative of progress of a chemical reaction, and stored programming capable of determining an end point value for the observable from the measurements.