Free Diet Carbon Footprint calculator with clear step-by-step results.
Applies published life-cycle emission factors to four food groups whose intensities differ by more than thirty-fold - roughly 30 kgCO2e per kilo for beef against 0.9 for plant foods. The intensity figure shows why the composition of a diet matters far more than its total weight.
Weekly footprint
kgCO2e = beef x 30 + pork/poultry x 6.5 + dairy x 3.2 + plant x 0.9
Annual footprint
Tonnes = weekly kgCO2e x 52.14 / 1000
They are rounded medians from global life-cycle assessment syntheses covering farm to retail. Individual products vary widely with system, region and feed.
Usually only marginally. Transport is typically under 10% of food emissions, so switching what you eat moves the number far more than switching where it came from.