Fifteen-bar percentage is estimated after desorption of a wet soil by hectorite for a specified time that varies with the amount of organic matter, clay, and pyroclastics and with the dominant mineral in the soil. The determination can be completed within 26 to 36 hr. Two simple procedures for drying the soil at 105°C are presented. The method for estimating 15-bar percentage should be useful to soil scientists at field facilities as a criterion in soil classification and for estimating wilting percentage.