How this instrument works
Diet is one of the biggest levers an individual has over their personal carbon footprint, and the size of the gap between diet types is larger than most people expect. Scarborough, Appleby, Mizdrak et al.'s 2014 study in Climatic Change, drawing on the large EPIC-Oxford cohort, measured mean dietary greenhouse gas emissions per 2,000 kcal/day across self-reported diet groups, age- and sex-adjusted for a fair comparison.
The published figures: high meat-eaters (≥100 g meat/day) at 7.19 kg CO2e/day, medium meat-eaters (50-99 g/day) at 5.63, low meat-eaters (<50 g/day) at 4.67, fish-eaters at 3.91, vegetarians at 3.81, and vegans at 2.89 kg CO2e/day — meaning the average high meat-eater's diet carries roughly two and a half times the daily footprint of the average vegan's diet.
This calculator takes the gap between your chosen baseline diet and the vegan figure of 2.89 kg CO2e/day, multiplies it by the number of days you've followed a vegan diet, and gives you the total CO2e emissions avoided — a concrete number for a change that's often described only in vague terms like 'better for the planet.'
- Choose the Diet you switched from — high, medium, or low meat-eater, fish-eater, or vegetarian.
- Enter Days followed a vegan diet — the period you want to total.
- Read CO2e saved vs. the baseline diet — the total kilograms avoided over that period.
Worked example — a year of vegan eating after a high-meat diet
Per Scarborough et al. (2014), a high meat-eater's diet averages 7.19 kg CO2e per day, versus 2.89 kg CO2e per day for a vegan diet at the same 2,000 kcal/day basis — a gap of 4.30 kg CO2e per day.
Someone who switched from a high-meat diet to fully vegan and kept it up for a full 365-day year saves 365 × 4.30 = 1,569.5 kg CO2e over that year — over 1.5 tonnes of CO2-equivalent, purely from the dietary shift, without changing anything else about their lifestyle.
Questions
How much CO2e does a vegan diet actually save compared to eating meat?
Per Scarborough et al.'s 2014 EPIC-Oxford study, the gap depends on which diet you're comparing against: about 4.30 kg CO2e/day less than a high meat-eater's diet (7.19 vs 2.89 kg CO2e/day), about 2.74 kg/day less than a medium meat-eater's, and a smaller 0.92 kg CO2e/day less than a vegetarian's, since vegetarian diets are already fairly low-emission. All figures are age- and sex-adjusted means at a standardized 2,000 kcal/day.
Why does a vegetarian diet still have a higher footprint than a vegan one?
Because dairy and egg production still carry meaningful greenhouse gas emissions — dairy cattle in particular produce methane, a potent greenhouse gas, through digestion, and both dairy and egg farming require land, feed, and energy inputs similar in kind (if generally smaller in scale) to meat production. The study found vegetarians at 3.81 kg CO2e/day versus vegans at 2.89 — a real but comparatively modest gap next to the much larger difference from cutting out meat entirely.
Does this account for how food is grown, packaged, or transported?
Yes, in aggregate — the Scarborough et al. figures are full dietary greenhouse gas emissions estimates covering the production, processing, and supply chain of self-reported diets, not just farm-level emissions. They don't isolate any single stage (like transport alone or packaging alone); they represent the whole footprint of what a typical person in each diet category actually ate.
Is this study still relevant, or has it been superseded?
The 2014 Scarborough et al. study remains one of the most widely cited direct empirical comparisons of dietary greenhouse gas emissions across meat-eating, fish-eating, vegetarian, and vegan diets specifically because of its large EPIC-Oxford cohort size and rigorous adjustment for age and sex. Food-system emissions factors do shift over time with changes in farming practice and supply chains, so treat the exact figures as a well-grounded reference point rather than an unchanging constant.
Does eating vegan for just a few days a week still add up?
Yes — because the formula is linear in days, even partial adoption counts proportionally: someone eating vegan just one day a week (52 days a year) instead of a high-meat diet the rest of the time still saves 52 × 4.30 ≈ 224 kg CO2e a year from that single weekly change, without needing to convert to a fully vegan diet to see a real, calculable benefit.