Vegan Calculator

A vegan calculator that takes what you eat in a typical week and where you live, and works out the greenhouse gas emissions of those foods, what the average person in your country eats, and what the same diet would cost if you went vegetarian or vegan. If you are already vegan or vegetarian, tell it for how long and it adds up what you have saved so far.

The core food factors are from Our World in Data. The footprint of each food per kilogram and per 100 grams of protein is the Poore & Nemecek (2018) meta-analysis of about 38,700 farms in 119 countries, published in Science, as charted by Our World in Data. What the average person in each country is supplied is the FAO Food Balance Sheets, also as published by Our World in Data. Farmed-fish counts use Fishcount’s estimate over FAO aquaculture production. Portion sizes, the plant-protein basket and the beef-herd split are stated modelling assumptions. The page lists every chart it uses, with a link, at the bottom.

It depends on what you ate before. For the average diet in a high-income country the calculator lands between one and two tonnes of CO2-equivalent a year once the protein is replaced with plant foods; for the world average it is under a tonne, because the world average eats far less meat than a European or an American. A kilogram of beef alone is about 99 kg of CO2-equivalent, so how much beef was on the plate decides most of the answer.

Because that is what happens. Nobody who stops eating meat eats the same plate with a gap in it; the protein and the calories come from somewhere else. Most vegan calculators report the drop as if the food simply vanished, which overstates the saving. This one replaces every gram of animal protein removed with a basket of plant proteins — tofu, pulses, peas, grains, nuts — priced on Our World in Data’s per-100-grams-of-protein charts, and replaces milk with a plant milk litre for litre. The figure without replacing anything is shown too, labelled as such, so you can see the difference.

As accurate as the best global data allows, and honest about where that stops. The footprints are global averages per food: beef raised in one country is priced the same as beef raised in another, because that is the resolution of the source. The country averages are food supply, which counts what reaches the shops including what gets thrown away after that, so they run a little higher than what people actually eat. The less-or-more control works in shares of that country figure, so no portion size touches it; the gram sizes are ours, only convert a typed count of portions into kilograms, and you can change every one of them. A large UK study (Scarborough et al., 2023, in Nature Food) found vegans at about a quarter of the diet emissions of high meat-eaters, and this calculator lands in the same range for a comparable diet.

Beef, by a wide margin: about 99 kg of CO2-equivalent per kilogram from beef herds and 33 kg from dairy herds, according to Poore & Nemecek. Lamb is about 40 kg, cheese 24 kg, farmed prawns 27 kg, farmed fish 14 kg, pork 12 kg, chicken 10 kg and eggs under 5 kg. Most plant foods are below 2 kg per kilogram, and pulses, nuts and vegetables well under 1 kg.

It gets most of the way there if the meat being replaced was beef and lamb, and much less far if the meat was chicken and the cheese stays. Cheese is one of the highest-impact foods per kilogram — about 24 kg of CO2-equivalent, more than pork or chicken — so a vegetarian diet heavy in cheese can cost more than a diet with a little chicken in it. The calculator shows both so you can see which foods carry your number.

Less than switching away from dairy does. Our World in Data’s comparison puts dairy milk at about 3.2 kg of CO2-equivalent per litre, rice milk at 1.2, soy at 1.0, oat at 0.9 and almond at 0.7. Almond milk uses the most water of the plant milks and rice milk the most emissions, but every one of them is a fraction of dairy on every measure.

Because the average person in a high-income country eats a lot of meat and dairy: Germany supplies about 88 kg of meat and 270 kg of milk equivalent per person per year, the United States about 124 kg of meat, and the world average about 43 kg of meat. The country figures are food available for consumption from the FAO Food Balance Sheets, which includes food wasted at the retail and household level, so the true intake is somewhat lower. The calculator says so where it shows the figure.

Bread, rice, pasta, vegetables, fruit, oils and everything else that stays on the plate whichever diet you follow. Those are the same in every scenario, so adding them to every bar would change the totals without changing the comparison. The calculator counts the foods that change when you go vegetarian or vegan, and what replaces them.

No — and no calculator using public data can. Poore & Nemecek publish one global mean per food, so the country you choose changes which average diet you are compared with, not the carbon cost of a kilogram of beef. Where you buy your food matters far less than what you buy: transport is typically under a tenth of a food’s footprint, and for beef it is under one percent.

Your saving per year is the difference between the diet you left and the vegan diet, and the total is that figure times the years you have been vegan. In normal mode the diet you left is your country’s average; if that is not what you ate, switch on advanced mode and enter it. The country average is taken at its latest year rather than tracked year by year — it moves little, and tracking it would claim a precision the answer does not have.

Poore & Nemecek measured five: greenhouse gas emissions, land use, freshwater withdrawals, scarcity-weighted water use and eutrophying emissions. The calculator shows four: scarcity-weighted water is left out because Our World in Data’s chart of plant-based milks has no such column, so a vegan’s milk cannot be priced on it, and guessing would break the rule that every number here is OWID’s.

Because a dairy cow’s emissions are shared between the milk and the meat she produces, while a beef-herd animal is raised for meat alone. Poore & Nemecek report 99 kg of CO2-equivalent per kilogram from beef herds and 33 kg from dairy herds. The FAO figures do not say which herd a country’s beef came from, so the calculator prices a kilogram of beef as 60 percent beef herd and 40 percent dairy herd, and says so.

Beef from a beef herd is about 99 kg of CO2-equivalent per kilogram, beef from a dairy herd 33 kg, lamb 40 kg, farmed prawns 27 kg, farmed fish 14 kg, pork 12 kg and chicken 10 kg — Poore & Nemecek’s global means, as charted by Our World in Data. Per 100 grams of protein the order holds but the gaps narrow, and that is the comparison the calculator prices on, because protein is what the plant foods replace. The per-kilogram and per-protein charts are both on the page, under “The data behind it”.

On Our World in Data’s per-100-grams-of-protein chart: nuts and peas at well under half a kilogram of CO2-equivalent, other pulses just under one kilogram, tofu about two, and grains just under three. Eggs are about four, poultry and farmed fish about six, pork about eight, milk about nine, cheese about eleven, dairy-herd beef seventeen and beef-herd beef fifty. The calculator’s plant basket is a mix of the first five.

The calculator counts land animals slaughtered for the meat in a diet, using two Our World in Data charts: the yearly number slaughtered by type and tonnes of meat produced by type, both from FAO. Dividing one by the other gives animals per kilogram — a kilogram of chicken is roughly half a bird, a kilogram of pork about one hundredth of a pig, and a kilogram of beef about one two-hundredth of a cow. Farmed fish are also counted using Fishcount’s midpoint estimate over FAO aquaculture production, because the food-footprint model also prices fish as farmed. Prawns, laying hens and dairy cows are not counted, so the real number is higher.

Yes. Everything you enter is written into the page address as you change it, so copying the link shares the exact comparison, country and years included. Nothing is stored anywhere else.