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Snow Water Equivalent Calculator

Work out snow water equivalent instantly with clear inputs, formula shown and shareable results.

About Snow Water Equivalent Calculator

Snow water equivalent is depth times the ratio of snow density to water density. Eighty centimetres of settled snow at 250 kg/m3 melts to 200 mm of water, or 200 litres per square metre. Fresh powder can be as light as 50 kg/m3 - a 10:1 depth ratio - while spring corn snow reaches 500 kg/m3.

Formulas

Snow water equivalent

SWE(mm) = depth(mm) x snow density / 1000

Depth ratio

fresh snow about 10:1, settled 4:1, wet snow 2:1

Worked example

With the default values below, Snow Water Equivalent Calculator returns Snow Water Equivalent of 200.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Snow depthminimum 0 cm
80 cm
Snow densityminimum 0 kg/m3
250 kg/m3

Results

Snow Water Equivalent
200.00 mm
Water Per Square Metre
200.00 L
Density Relative To Water
0.250
Equivalent Water Depth
20.00 cm

Step by step

  1. 1Values used
  2. 2Snow water equivalent
  3. 3Depth ratio
  4. 4Snow Water Equivalent= 200.00 mm
  5. 5Water Per Square Metre= 200.00 L
  6. 6Density Relative To Water= 0.250
  7. 7Equivalent Water Depth= 20.00 cm

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does snow density vary so much?

Fresh crystals trap enormous air volume, then settle, sinter and refreeze. Density typically triples between fresh fall and spring melt.

Why does SWE matter for water supply?

Because mountain snowpack is a natural reservoir. SWE, not depth, tells water managers how much runoff to expect.

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