Weigh your five-gallon bucket and record the weight.
Use a ruler to measure the top surface of snow in a particular spot. Make sure the snow is flat on top and at least a foot deep. Place your ruler into the snow to the ground and level out your area until about an 18-inch square is exactly as tall as your ruler.
Place the ruler in one spot on top of the snow, mark both ends, and place the ruler three more times at 90-degree angles, so that you have a square shape marked off in the snow. Each side of the square should be exactly a foot long.
Use your shovel to dig out the square that you have marked in the snow completely, adding as little snow from outside the square as possible. Put all of your snow into a bucket.
Place the bucket of snow indoors and allow it to melt. Place it by a fire or a heater, or let it sit overnight to melt. The snow will now be just water.
Place the bucket on a scale and record the weight registered on the scale. Subtract the weight of the bucket determined in step one from this new result, and you will have the weight of one square foot of the snow that you shoveled into your bucket. You can now use math to determine the amount of snow on your roof or driveway, or any other collection of snow.