This paper describes a method for estimating the depth of new snow, using hourly data of total snow depth and precipitation. As the snow cover is compacted continuously due to its own weight, the depth of new snow deposited since the previous time-step to the present time is given by a difference between the height of the present snow surface and the present is impacted height of the previous snow surface. Thus, based on viscous compression theory and an empirical relation between compressive viscosity and the density of snow, an equation has been derived to compute the time variation of the thickness of a snow layer due to viscous compression. Using this equation, the present height of the previous snow surface, which cannot be measured by simple means, was computed and the depth of daily new snow was estimated as its difference from the present measured total snow depth. The approximated results were found to be in good agreement with data measured in Tohkamachi during the three winters from 1992–93 to 1994–95. The standard deviation was 1.71 cm and the maximum difference between estimated values and observed values was ± 8 cm.