A rather surprising fact I discovered while checking the Exercise & Activity Calculator: four hours of downhill moderate effort Skiing, burns only  calories 1,776.00.

I thought: shame the calculator doesn’t have a snowboarding calculation section.

Then, I remembered that that’s the Internet of the 21st century - surly there’s a calculator that does include snowboarding.
So, I fired up a Google search, which gave me there calculators for snowboarding:

self.com seems to be geared only towards women.

sparkpeople.com seems to be geared towards North Americans only (they only calculate in pounds).

But glamour.com gave me the answer: 

 You burn 1864.8 calories during 240 minutes of Snowboarding.

So, even though it’s a bit more strenuous than skiing, still not much of an excersise.

But then, who goes snowboarding for the exercise?!