Our Calculations
The results in the Impact Box are calculated on the following basis:

	Hamburger: the savings from skipping one beef meal (approximately 1/3 pound).
	Paper: the percentage of post-consumer waste in the paper you buy.
	Light Bulb: the energy savings over the life of an efficient light bulb (approximately 7 years more than a traditional bulb).
	Showerhead: the amount of water saved annually by an efficient showerhead.

How does it work?
How, exactly, does giving up a hamburger or changing to an energy-efficient light bulb total "1,000 gallons of water" or "1,000 pounds of CO₂"? It's in the process.

For example, when you give up a hamburger, water is saved in a variety of steps:

	for the cow to drink
	for the grain to grow
	for the beef to be ground

We researched each of these processes to get reliable data, and you can take a look at the specific sources.

Everyone knows that paper is made from trees.

	One ream of printer paper (500 sheets) uses 6% of an average-sized tree's wood.
	One tree produces about 17 reams of printer paper, or about 8,500 sheets.

The average person in the United States uses 750 pounds of paper per year—the equivalent of 9 trees. That means we go through over two and a half billion trees each year (281 million people x 9 trees per person = 2,529,000,000 trees).

Water Weight
The average bathtub holds 52 gallons of water. That means it takes more than 11 bathtubs of water to make 1 burger (600 gallons per hamburger/52 gallons per bathtub = 11.5 bathtubs).