Abstract: In routine design of sand drains, mean consolidation degree and mean strength increase are estimated, using only horizontal coefficient of consolidation. In this paper, it is suggested to compute consolidation degree at any time at any depth of subsoils by use of three dimensional consolidation theory. It was shown that the results estimated by such appproach are more accurate. Some graphs for computation prepared with computer were presented. Finally, two illustrative example by means of such graghs were given.