How to Calculate Your Food Carbon Footprint

For each food you want to include:

1. Quantity — kilograms bought (or eaten) over a period, usually a week, then scaled to a year.
2. Factor — kg CO₂e per kg of that food, from one dataset.
3. Emissions — quantity × factor.
4. Total — the sum across foods.

Use one dataset for every food so the boundaries match. Mixing a factor that includes land-use change with one that does not makes the comparison meaningless.

Most food factors are lifecycle values: they add up emissions across the supply chain rather than measuring one stage. Depending on the dataset, that can include:

• Land-use change — carbon released when land is converted to farmland, where the dataset includes it.
• Farm stage — fertiliser production and use, machinery fuel, animal feed, rice paddies and livestock.
• Processing — energy used to turn crops and animals into products.
• Transport — moving food along the supply chain.
• Packaging and retail — including refrigeration in shops.

Cooking and storage at home are usually outside these boundaries. Check the dataset's documentation for its exact scope.

Much of food's climate impact is not carbon dioxide. Methane comes from ruminant digestion (cattle, sheep), manure and flooded rice. Nitrous oxide comes mainly from fertilised soils and manure. CO₂e (carbon dioxide equivalent) converts these gases to one scale using global warming potentials, so a factor in kg CO₂e covers all three. A CO₂-only figure would leave out most of the impact of some foods, so do not compare CO₂ and CO₂e numbers directly.

The values below are from Poore & Nemecek (2018), *Science*, via Our World in Data: global mean greenhouse-gas emissions per kg of food product, in kg CO₂e, across the supply chain including land-use change, with a 2010 reference year. They are averages over very different producers; they are not universal values and not the footprint of any specific product you buy.

The same dataset reports wide ranges within each food, not just between foods. The main reasons:

• Production method and farming system — feed, fertiliser use, manure handling and yields differ between farms.
• Geography — climate, soils and whether land was recently converted.
• Supply chain — processing, storage and transport mode. Air-freighted produce is a different case from food shipped by sea.
• Food waste — food that is bought and thrown away still carried its production emissions. Estimating from purchases captures this; estimating from what is eaten does not.
• Factor methodology — boundaries (land-use change included or not), allocation between co-products such as milk and beef, and the reference year.

This is why one global number should not be treated as correct for a particular product. If a producer publishes a product-specific lifecycle assessment, check its scope before comparing it with a dataset average.

Illustrative quantity, not a recommendation: 0.2 kg per week of one food, which is 0.2 × 52 = 10.4 kg per year. Using the global mean factors above:

• Whole household footprint — the carbon footprint guide explains how food combines with energy, travel and goods without double counting. The Carbon Footprint calculator covers home energy, heating, car and flights; it does not calculate food, so add a food estimate separately and label it.
• A reduction plan — the carbon reduction planning guide.
• Travel — the transport carbon footprint guide.

The Carbon Footprint hub collects all carbon tools and guides; the methodology page documents the sources used on this site.