- What data is this calculator based on?
- The core numbers come from Scarborough et al. (2023), "Vegans, vegetarians, fish-eaters and meat-eaters in the UK show discrepant environmental impacts," published in Nature Food. It linked the real diets of 55,504 people to food-level environmental data from 570 life-cycle assessments covering more than 38,000 farms in 119 countries. The study reports dietary greenhouse-gas emissions per day for each diet type, which is what we multiply by the number of days you've eaten vegan. Broader context on land and water comes from Poore & Nemecek (2018) in Science.
- How much CO₂ does going vegan actually save?
- In the Nature Food study a vegan diet produced about 2.47 kg CO₂e per day versus 10.24 kg for a high-meat diet (100 g+ of meat a day). That difference — roughly 7.8 kg a day — adds up to around 2.8 tonnes of CO₂e per year. Against a lighter previous diet the saving is smaller: a vegetarian switching to vegan saves closer to 1.7 kg a day. Pick the diet that matches your old eating to get a realistic figure.
- Why are your numbers lower than other vegan calculators?
- Many popular vegan calculators use figures traced back to the documentary Cowspiracy — for example 4,164 litres of water and one animal saved per day — which aren't peer-reviewed and are widely disputed. We deliberately use published, peer-reviewed research instead. That makes some numbers more modest (a vegan diet uses about 54% less water than a high-meat one, not 90%+), but every figure here is one you can cite.
- How is "animals saved" calculated?
- It's an estimate of farmed land animals, scaled from FAOSTAT and Faunalytics global slaughter data — roughly 30 land animals a year for a typical high-meat diet, and fewer for lighter diets. It's genuinely hard to pin down: published estimates range from about 30 land animals to over 100 when fish and shellfish are included. Because aquatic animals are so numerous and so variable, we don't count them here, so the real total is higher. Treat the number as a conservative order-of-magnitude figure, not a precise count.
- Does a vegan diet really use less land and water?
- Yes. In the same Nature Food study a vegan diet had about 75% less land use, 54% less water use, 73% less water pollution (eutrophication) and 66% less impact on wildlife than a high-meat diet. Poore & Nemecek's global analysis reached similar conclusions, estimating that a shift away from animal products could cut agricultural land use by around 75%.
- Should I pick my previous diet or my current one?
- Pick the diet you're replacing — the one you ate before going vegan (or the one you'd otherwise eat). The calculator shows what you save by being vegan instead of that diet, so the baseline is what you're comparing against, not your vegan diet itself.
- Is the vegan impact calculator free and private?
- Yes. It's free, needs no sign-up, and runs entirely in your browser — your inputs are saved only to this browser's local storage and never uploaded.