Snow to Liquid Ratio Calculator
The snow-to-liquid ratio (SLR) measures how much snow falls per inch of liquid precipitation, reflecting snow density. The traditional "10 inches of snow per inch of rain" rule of thumb is only an average: actual SLR varies from about 4:1 for heavy wet snow near 32 F to 30:1 or more for extremely cold, powdery snow. The snow water equivalent (SWE) is the liquid depth contained in a snowpack, the critical measure for water supply and flood management. Enter the snowfall depth and liquid equivalent to compute SLR and snow density, or enter SLR and SWE to estimate snowfall depth.
Snow-to-liquid ratio formula
SLR = Snow Depth / Liquid Equivalent
Snow Density (kg/m3) = 1000 / SLR
SWE (in) = Snow Depth / SLR
SLR is dimensionless (both inputs in the same units). Snow density of 1,000 kg/m3 would be pure liquid water; fresh snow density of 50-150 kg/m3 corresponds to SLR of 7:1 to 20:1. The NWS measures liquid equivalent using a heated rain gauge or by melting a snow core from a snow board.
SLR guidelines by temperature
- Near 32 F (0 C): SLR approximately 5:1 to 8:1 (wet, heavy snow).
- 25-30 F (-4 to -1 C): SLR approximately 10:1 to 15:1 (typical winter snow).
- 15-25 F (-9 to -4 C): SLR approximately 15:1 to 20:1 (dry, fluffy snow).
- Below 15 F (below -9 C): SLR approximately 20:1 to 30:1 or more (powdery, very low density).
Snow-to-liquid ratio: frequently asked questions
What is the snow-to-liquid ratio?
The snow-to-liquid ratio (SLR) is the depth of snow that results from a given amount of liquid precipitation. For example, the traditional rule of thumb is a 10:1 ratio, meaning 1 inch of rain would produce 10 inches of snow. However, actual SLR varies widely from about 4:1 for wet, heavy snow to 30:1 or more for light, fluffy snow at very cold temperatures.
What determines the snow-to-liquid ratio?
Temperature is the primary factor: cold temperatures produce dry, fluffy snow with high SLR (low density); near-freezing temperatures produce wet, dense snow with low SLR. The 10:1 ratio applies near 28-30 F. Below 15 F, SLR typically exceeds 15:1. At 32 F or above (wet snow), SLR can be as low as 4:1 to 6:1.
What is snow water equivalent (SWE)?
Snow water equivalent is the depth of liquid water that would result if a given snowpack were completely melted. SWE is the critical hydrological variable for water resource management, flood forecasting, and ski resort operations. NOAA and the Natural Resources Conservation Service (NRCS) maintain a network of SNOTEL (Snow Telemetry) stations that measure SWE continuously in mountainous western US watersheds.
Why is the 10:1 rule often wrong?
The 10:1 ratio is a climatological average derived from historical records at stations with moderate winters. It can be significantly wrong for individual events. The NWS now trains forecasters to estimate SLR based on atmospheric column temperatures and snow crystal type. Heavy wet snowstorms near 32 F may produce ratios of 5:1 to 8:1, while Arctic air masses can produce ratios of 20:1 to 30:1.
How is snow density related to SLR?
Snow density (kg/m3 or lb/ft3) is inversely related to SLR. Liquid water density is approximately 1,000 kg/m3. If SLR = 10, snow density = 1,000/10 = 100 kg/m3 (10% of water). If SLR = 20, snow density = 50 kg/m3. Fresh fallen snow ranges from about 50-150 kg/m3; settled or wet snow can be 200-400 kg/m3; slush can approach 700-800 kg/m3.
Official sources
- NOAA/NWS: Snow-to-Liquid Ratio.
- NRCS SNOTEL: Snow Water Equivalent Data.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.