Snow Water Equivalent Calculator
Calculate snow water equivalent (SWE) from snow depth and snow-to-water ratio. Used in hydrology, flood forecasting, and water supply management.
SNOW WATER EQUIVALENT
1 inches of water
IN mm
25.4 mm
SNOW DENSITY
83 kg/mΒ³
Snow Density β Common Ratios
| Snow Type | Ratio | Density (kg/mΒ³) |
|---|---|---|
| Light/fluffy (powder) | 20:1 | 50 |
| Average fresh snow | 12:1 | 83 |
| Wet/packing snow | 8:1 | 125 |
| Heavy/wet snow | 5:1 | 200 |
| Settled/old snow | 4:1 | 250 |
| Firn (compacted) | 2:1 | 500 |
π‘ How to Calculate Snow Water Equivalent
What Is Snow Water Equivalent?
Snow water equivalent (SWE) tells you how much liquid water is stored in a snowpack. It is the depth of water that would result if the entire snowpack were melted instantly. SWE is critical for flood forecasting, reservoir management, and water supply planning in regions that depend on snowmelt for their water supply.
How to Calculate SWE
Snow Water Equivalent Formula
The snow-to-water ratio varies widely depending on snow type:
- Wet, heavy snow: 3:1 to 5:1 (3β5 inches of snow = 1 inch of water)
- Average fresh snow: 10:1 to 15:1
- Light, dry powder: 20:1 to 30:1
Worked Example
12 inches of average fresh snow with a 12:1 ratio:
SWE = 12 / 12 = 1 inch of water
The same 12 inches of wet snow at 5:1 = 2.4 inches of water. This illustrates why wet snow causes more flooding β it contains much more water per inch of depth. See our snow weight calculator to find the actual load on a roof.