What you eat is one of the largest parts of a personal carbon footprint, and the difference between food types is enormous — a kilogram of beef can carry thirty times the emissions of a kilogram of beans. This calculator turns your weekly eating habits into an annual CO2e figure using peer-reviewed lifecycle data.
How it works
For each food category the calculation is simple and transparent:
category annual CO2e = weekly servings × serving size (kg)
× emission factor (kg CO2e per kg)
× 52 weeks
total = sum of all categoriesEmission factors come from the Poore and Nemecek lifecycle dataset, the most comprehensive available, and each is paired with a realistic serving size so a serving of steak and a serving of lentils are compared fairly.
Example and tips
Eating beef four times a week alone contributes roughly 1,250 kg CO2e a year — often more than every other food category combined for a typical eater. Swapping half of those beef meals for poultry cuts that to about 750, and swapping them for legumes drops it under 100. The highest-leverage changes are almost always reducing beef and lamb first; dairy is the next largest lever, while vegetables, grains, and legumes barely move the total.
Why beef is so much higher than other foods
Beef carries the highest emission factor of any common food category for three compounding reasons. First, cattle are ruminants — they digest grass and feed through fermentation in their stomachs, releasing methane, a potent greenhouse gas. Second, cattle require large amounts of land, both as pasture and to grow their feed grain, and land use change (deforestation to create farmland) is itself a major source of emissions attributed to beef. Third, the feed-conversion ratio for beef is poor: a large amount of grain must be consumed to produce a kilogram of beef, multiplying the embedded agricultural emissions from the feed crop.
The contrast with legumes is stark. Beans and lentils fix nitrogen from the atmosphere (reducing the need for synthetic fertiliser), require relatively little land, and produce no methane. This explains why the Poore and Nemecek data consistently places beef at roughly 60 kg CO2e per kilogram while most legumes fall under 2 kg CO2e per kilogram.
Food category comparison
The approximate emission factors from the Poore and Nemecek dataset (per kilogram of food, median values):
| Food category | Approx. kg CO2e per kg |
|---|---|
| Beef (beef herd) | ~60 |
| Lamb and mutton | ~24 |
| Farmed prawns | ~18 |
| Cheese | ~11 |
| Pork | ~7 |
| Chicken | ~6 |
| Eggs | ~4.5 |
| Fish (wild) | ~3 |
| Milk | ~3.2 |
| Tofu | ~3 |
| Rice | ~2.7 |
| Legumes (beans, lentils) | ~0.9 |
| Vegetables | ~0.4 |
| Fruit | ~0.4 |
These are approximate medians. Actual values vary by production system, country, and farming practice — grass-fed beef in some regions has a lower footprint than feedlot beef, and air-freighted produce has a much higher footprint than seasonally grown local equivalents.
What this calculator doesn’t include
The calculation covers the food production system through retail — growing, processing, packaging, and transport to the shop. It does not include:
- Cooking energy — gas or electric hobs and ovens add to your personal footprint but vary widely by energy source
- Food waste — food you buy but throw away still carries the full production footprint; wasted beef is a double loss
- Packaging — plastic and cardboard packaging adds emissions beyond the food itself
- Restaurant meals — portion sizes and preparation methods vary enough that they are hard to model from a serving count
Treat the result as a conservative baseline for the food production part of your diet footprint.