I've always wanted to know how much precipitation (in rain mm) is
required to produce 1 foot of snow.

I've heard statements such as "1 foot of snow is equivalent to 1 inch
of rain" (ie: 12:1 ratio)
Ive also heard "1mm of rain is equivalent to 1cm of snow" (ie: 10:1
ratio)
Which one is correct?

In order to get the answer I performed the following experiment...

I took a pint beer-glass (one with an official pint crown and is 1
pint to the rim, not a lined glass)

I filled it as best as I could with snow, taking care not to get
air-gaps and also care not to compress the snow. The snow must be kept
"fluffy" and not compacted in.

I skimmed the top of the glass so that I have a pint of fluffy snow.
I brought the glass indoors and watched my pint of snow melt.

I was surprised how little water there was left in the glass!
I measured the water (in ml) and divided that number in to 568ml (one
pint)

Before posting my result, I'd be interested to see if somebody else
could perform the same experiment and we will then compare our
answers.

Its just a bit of fun,

regards

Brendan