How much water is in the snow?
Enter snow depth and density to get the depth of water, or the water you need to see how much snow to melt.
This is a planning aid, not a safety assessment. It says how much water is in snow, not how safe the snow is: it is no substitute for an avalanche forecast, training and judgment in the mountains. Treat melted snow before drinking if it may be contaminated. How we check our calculators.
Density is the share of the snow's volume that would be water. The last field is used only with "My own value".
What snow water equivalent means
Snow is mostly air. Fresh powder may be 90 percent air by volume, and the same snow, weeks later, packed and refrozen, may be 60 percent air. What is left is water, and the depth of that water layer is the snow water equivalent, or SWE. Hydrologists use it to forecast spring runoff; campers and winter hikers use the same idea for a practical question: how much snow do I have to melt for a pot of water?
The formula
SWE = snow depth × density, with density written as a fraction (10 percent is 0.10), and the answer in the same unit as the depth. For the reverse question, snow volume = water volume ÷ density, and the snow weighs the same as the water, since melting changes its volume and not its mass. A liter of water weighs a kilogram, so a liter of melt water means a kilogram of snow, however many liters of snow that takes.
Worked example
The Wyoming State Engineer's page gives this one: 25 inches of new powder at 10 percent density has an SWE of 2.5 inches. After settling, 60 inches of snow at 30 percent density holds 18 inches of water. In metric, 60 cm of new snow at 10 percent is 60 mm. To get a gallon of water by melting, you need 10 gallons of new snow, 3.3 gallons of settled snow or 2.5 gallons of dense spring snow.
| Kind of snow | Density | Snow for 1 gal of water |
|---|---|---|
| New snow | about 10% | 10 gal |
| Settled snowpack | about 30% | 3.3 gal |
| Spring snowpack | about 40% | 2.5 gal |
Where the density values come from
The Wyoming State Engineer's Office says new snow commonly has a density of 8 to 10 percent of water and that settled snow reaches about 30 percent. The 40 percent figure for spring snow comes from NRCS pages, which report densities of 40 percent or more in late March and early April; the other NRCS statements we found say new snow runs from about 5 percent in cold air at 14 °F to about 20 percent near freezing. We read these NRCS statements in search results, not on the pages themselves, so treat the preset values as typical rather than exact and use your own measurement when you can. Density depends on region, temperature, wind and age.
Limits of this method
- One density for the whole pack. A real snowpack has layers, and the old, dense layers near the ground hold much more water per inch than the fresh powder on top. Use a core or an average for a deep pack.
- Snow depth varies. Wind packs snow into drifts and strips it from ridges. A single depth reading does not describe a basin.
- It is not a safety tool. SWE tells you nothing about avalanche danger or ice thickness. Use local forecasts, training and judgment.
- Melting costs fuel and time. The calculator gives the snow, not the fuel. The propane calculator can help with stove fuel.
Common questions
What is snow water equivalent?
It is the depth of water you would get if the whole snowpack melted at once. The Wyoming State Engineer's Office, which runs a snow survey, defines it as the product of snow depth and snow density. It is what water managers track, because a deep layer of light snow can hold less water than a shallow layer of heavy snow.
How much water is in 10 inches of snow?
For new snow, about an inch: Wyoming gives a density of around 8 to 10 percent for new snow, so 10 inches holds 0.8 to 1 inch of water. After the snow settles, the density rises to about 30 percent, and 10 inches then holds about 3 inches. The NRCS pages found in our search report densities near 40 percent in spring. The density is the number that matters, so measure it if you can.
How do I find the density of snow?
Snow surveyors take a core of known volume and weigh it; the density is the weight of the core divided by the weight of the same volume of water. A rough field way is to melt a known volume of snow in a measuring pot and note how much water you get, then divide the water by the snow. The presets on this page are the typical values; replace them with your own measurement.
How much snow do I need to melt for a gallon of water?
At 10 percent density, about 10 gallons of snow; at 30 percent, about 3.3 gallons; at 40 percent, 2.5 gallons. The snow weighs the same as the water it makes, 8.3 pounds for a gallon. Plan the fuel too, since melting takes a long time and a lot of heat.
Is melted snow safe to drink?
Not necessarily. Snow can carry dirt, animal waste and other contaminants. The Centers for Disease Control and Prevention says to boil water of uncertain quality for 1 minute, and 3 minutes above 6,500 feet.
Does snow water equivalent tell me if it is safe to travel?
No. It measures how much water is in the snow, not how stable the snow is. Avalanche danger depends on layers, slope, weather and recent loading, and needs a local avalanche forecast and training. This page is a planning aid for water.
This is a planning aid, not a safety assessment. It is not an avalanche, flood or water supply forecast. If you travel in snow country, take avalanche training and check the local avalanche forecast.
Sources: Wyoming State Engineer's Office, "Snow Water Equivalent (SWE)" (definition, SWE as depth times density, new-snow and settled-snow densities, the 25-inch example); USDA Natural Resources Conservation Service snow survey pages (Alaska and Nevada) for spring and new-snow densities, seen in search results only; Centers for Disease Control and Prevention, boil water guidance; U.S. Geological Survey, Water Science School (1 liter of water weighs 1 kilogram). Related: Trail Water Calculator, Propane Calculator, Density Calculator, Rainwater Harvesting Calculator, Altitude Pressure and Boiling Point Calculator.