Snow-to-Water Ratio Calculator

About this calculator

The snow-to-water ratio (SLR) expresses how many inches (or centimeters) of fresh snow correspond to one unit of melted liquid water — a widely cited rule of thumb puts the average at 10:1, but the real ratio swings anywhere from about 6:1 for wet, dense snow near freezing to 30:1 or higher for the driest powder that forms in very cold air, since colder temperatures produce more elaborate, air-filled snow crystals that pack less water into the same depth.

Meteorologists at the National Weather Service and other forecasting agencies use the snow-to-water ratio to convert forecast liquid precipitation into an expected snowfall depth, since precipitation models predict water content far more reliably than snow depth directly. Ski resorts and skiers reference the same ratio to judge whether incoming snow will be light, dry powder or heavy, wet snow, and hydrologists use it in reverse, measuring snow depth to estimate the water content that will feed spring runoff.

This calculator takes a fresh snow depth and its melted water equivalent and returns the snow-to-water ratio between them.