Nature Carbon Footprint Calculator - https://www.nature.org/en-us/get-involved/how-to-help/carbon-footprint-calculator/
Terrapass Carbon Footprint Calculator - https://www.terrapass.com/carbon-footprint-calculator
EPA Carbon Footprint Calculator - https://www3.epa.gov/carbon-footprint-calculator/data/GHGCalculator.xls
Terrapass Carbon Footprint Calculator - https://www.terrapass.com/carbon-footprint-calculator
EPA Carbon Footprint Calculator - https://www3.epa.gov/carbon-footprint-calculator/data/GHGCalculator.xls