To calculate carbon footprint you can employ these methods:
1. Life cycle assessment - please check ISO 14040/14044 https://www.iso.org/standard/38498.html
2. The GHG Indicator: UNEP Guidelines for Calculating Greenhouse Gas Emissions for Businesses and Non- Commercial Organisations - please check https://www.unepfi.org/publications/climate-change-publications/the-ghg-indicator-unep-guidelines-for-calculating-greenhouse-gas-emissions-for-businesses-and-non-commercial-organisations/