With Eco Tracker, you’re able to measure the ecological footprint of your production, form by form. You’ll be able to view breakdowns and totals of all the paper, carbon, and water saved by using Greenslate as your payroll provider, as well as the amount of carbon you’ve prevented from entering the atmosphere. Basis for Eco Tracker calculations:

Making 88 sheets of 20# 8.5″x11″ releases 1 pound of CO2
1 sheet – 1 88th of a pound (0.01136363636 / pound)
1 pound = 0.0005 US tons
therefore:
1 sheet of paper = 0.00005681818 tons / CO2

One tree can create 1 2/3 cartons or 16.67 reams of regular 8 1/2” x 11” copy paper
500 sheets per ream
Therefore:
8335 sheets per tree

1 sheet of paper = 0.00011318619 trees

1 sheet of paper takes 3 gallons of water to produce

Source: http://www.co2list.org/