Work out snow water equivalent instantly with clear inputs, formula shown and shareable results.
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.
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
Fresh crystals trap enormous air volume, then settle, sinter and refreeze. Density typically triples between fresh fall and spring melt.
Because mountain snowpack is a natural reservoir. SWE, not depth, tells water managers how much runoff to expect.