First, convert your current weight to kilograms
By dividing by 2.2.

Example 150# person = 68.2 kilo

Here are the conversions, you’ll have to decide how fast and intense you shoveled and also take into account how heavy the snow is.

The following numbers are based on ONE HOUR’s worth of work.
Take that into consideration on how long you shoveled.

Light Powdery snow, light effort (moving less than 10 pounds per minute) 
Use Kilo weight X 5.0= calories per hour

Quite a few inches of powder or couple inches of heavier snow (moving about 10-15 pounds per minute)
Kilo weight X 7.0 = calories per hour

Heavy wet snow, hard effort (moving over 16 pounds per minute)
Kilo weight X 9.0 = calories per hour

Brutal midwest and east coast “poundings” of wet snow OR the plow just came though and blocked your driveway (“I’m going to die” effort)
Kilo weight X 12.0 = calories per hour

Using a snow blower  4.5 X kilo weight = cals per hour

These factors I’m using are METS or metabolic equivalents determined by the American College of Sports Medicine