A method was proposed in a previous article (CRA, 22, 240-258, 1997) to estimate the state of incomplete adaptation by using the effective chromatic adaptation coefficient alpha(min). The method could be applied to any experiment on chromatic adaptation using object-color or luminous-color stimuli, but its computational procedure was rather tedious. For this reason, the two simple methods, Methods I and II, are proposed to give the approximate estimates of alpha(min). Method I uses the corresponding reference color under reference illuminant to a test achromatic color under test illuminant. Method II uses the two kinds of relation equations between rest adapting luminance and alpha(min). The estimates of alpha(min) by each of the two methods agree fairly well with those given in the previous article to the three experiments studied.