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Food Impact Calculator

What did you eat before?

100 g or more of meat a day — a typical Western meat-eater.

What do you eat now?

No meat, fish, dairy or eggs.

How long have you eaten this way?

Unit

Daily footprint, at 2,000 kcal

Before · High meat10.24 kg/day
Now · Vegan2.47 kg/day

CO₂e you've kept out of the air

2,838 kg

That's about 2.8 tonnes of CO₂e

Farmed animals spared

30

Land animals (estimate) — aquatic animals not counted

Days on this diet

365

Same as not driving

14,781 km

A year of CO₂ soaked up by

135 trees

Reference: a vegan diet vs a high-meat diet

75% less

Greenhouse gases

75% less

Land use

54% less

Water use

73% less

Water pollution

66% less

Wildlife loss

Per-person averages from Scarborough et al., Nature Food (2023) — 55,504 UK diets. Land, water and wildlife figures are published for this pairing only, so they don't change with your selection above.

How this is calculated & sources

CO₂e saved = (your previous diet − your current diet) × days. If your current diet emits more than your previous one the result flips to extra CO₂e released. Dietary greenhouse-gas emissions per day (kg CO₂e, at 2,000 kcal), from Scarborough et al. 2023:

  • High meat10.24 kg/day
  • Low meat5.37 kg/day
  • Pescatarian4.74 kg/day
  • Vegetarian4.16 kg/day
  • Vegan2.47 kg/day

Equivalents use 0.192 kg CO₂e per km for an average car and 21 kg absorbed per year by a mature tree. Farmed land animals spared are estimated from FAOSTAT/Faunalytics slaughter data (~30 land animals/year for a high-meat diet); fish and other aquatic animals are far more numerous and are not counted. The percentage panel above is from the same Nature Food study; broader context comes from Poore & Nemecek, Science (2018).

These are population averages and best-effort estimates, not a precise personal footprint.

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Nothing is uploaded. Just open it and start.

A food impact calculator, grounded in real research

Free, no sign-up. Compare what you eat now with what you used to eat and see the carbon dioxide and farmed animals you spare — or add — worked out from the peer-reviewed Nature Food study of 55,000 real diets, not the inflated numbers copied across most vegan calculators. Pick your previous diet, your current one, and how long you've eaten this way.

Peer-reviewed, not hype

Built on Oxford's Nature Food study, not the disputed figures most vegan calculators copy.

CO₂, land, water & animals

See emissions avoided, plus land, water and farmed-animal savings — with the sources shown.

Before vs now

Pick any two diets — high-meat through vegan — and see the difference, in either direction.

100% private

Every figure is worked out in your browser. Nothing is uploaded, no account needed.

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Frequently asked questions

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 your current diet. 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%.
What do "previous diet" and "current diet" mean?
Previous is what you used to eat; current is what you eat now. The calculator shows the difference between the two, multiplied by how long you've eaten your current diet. Going from a high-meat diet to a vegetarian one saves roughly 6 kg of CO₂e a day, for example, while going from vegetarian to vegan saves about 1.7 kg a day.
Can I compare going the other way, to a heavier diet?
Yes. If your current diet has a bigger footprint than your previous one, the result flips and shows the extra CO₂e released (and extra farmed animals) instead of a saving. The same data is used in both directions, so moving from vegan back to a high-meat diet adds exactly what the reverse move would save.
Is the food 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.

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