Vegan Diet Footprint Calculator (CO₂e, water & land saved by switching)

Understanding the vegan diet footprint calculator — concept and principle

This calculator estimates how much greenhouse gas, water, land use and water pollution a person or household could save by switching from their current diet to a vegan diet. It uses measured diets of tens of thousands of people in the UK.

Median UK diet footprints scaled to a year: switching cuts greenhouse gas by about two thirds.

How it is calculated

Yearly footprint = daily footprint for the diet × (your kcal ÷ 2,000) × 365.25 × people

Saving = current diet − vegan diet; cut (%) = (1 − vegan ÷ current) × 100

Median daily values at 2,000 kcal (Scarborough et al., 2023):

Greenhouse gas (kg CO₂e): high meat 10.24, medium meat 7.04, low meat 5.37, fish-eater 4.74, vegetarian 4.16, vegan 2.47.
Water use (L): 890, 780, 710, 710, 530, 410.
Land use (m²): 16.78, 11.28, 8.31, 6.31, 6.01, 4.37.
Eutrophication (g PO₄e): 40.80, 29.61, 23.55, 21.09, 17.27, 10.70.

The principle

The study linked what 55,504 people in the UK reported eating to environmental data from more than 38,000 farms in 119 countries. Animal foods need feed crops grown first and lose most of that energy along the way, and ruminants also release methane, so diets with more meat carry larger footprints for the same calories. Standardising to 2,000 kcal removes the effect of simply eating more. Scaling by your own intake assumes your diet has the same mix as the typical diet in that group.

Worked example

Default inputs: medium meat-eater, 2,000 kcal a day, 1 person.

Scaling factor = 2,000 ÷ 2,000 × 365.25 × 1 = 365.25 days.
Current diet = 7.04 × 365.25 = 2,571 kg CO₂e a year; vegan = 2.47 × 365.25 = 902.
Saved = 2,571 − 902 = 1,669 kg CO₂e a year; cut = 1 − 2.47 ÷ 7.04 = 65 %.
Water saved = (780 − 410) × 365.25 ÷ 1,000 = 135.1 m³ a year.
Land use cut = 1 − 4.37 ÷ 11.28 = 61 %; eutrophication cut = 1 − 10.70 ÷ 29.61 = 64 %.

Each point is the calculator re-run with only “Food energy per day (kcal)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Food energy per day (kcal)	Greenhouse gas saved per year (kg CO₂e)
500	417
1,000	835
1,500	1,252
2,000	1,669
2,500	2,086
3,000	2,504
4,000	3,338

How to read the result

The percentages are the most robust output: they compare medians within the same study. The tonnes and cubic metres are typical values for a diet group, and an individual's footprint can be well above or below them. Moving from a high-meat diet gives the largest cut; even a shift from medium to low meat or to vegetarian removes a large part of the difference. The figures cover food production only, not cooking, packaging at home or travel to shops.

Common mistakes

Treating the result as a measurement of your personal diet.
Comparing these numbers with studies that use different methods.
Forgetting that the data describe UK diets.

Keep in mind: These are median estimates for diet groups, not a nutrition plan. A vegan diet needs planning for nutrients such as vitamin B12; ask a doctor or dietitian if you have health conditions.

Frequently asked questions

How much CO₂ does going vegan save?

In this study a medium meat-eater's diet emits about 2.6 tonnes CO₂e a year at 2,000 kcal a day and a vegan diet about 0.9 tonnes.

Is a vegetarian diet much better than a meat diet?

Yes, by these medians: about 4.16 vs 7.04 kg CO₂e a day for a medium meat-eater.

Sources: Scarborough P., Clark M., Cobiac L., et al. (2023), "Vegans, vegetarians, fish-eaters and meat-eaters in the UK show discrepant environmental impacts", Nature Food 4: 565–574

Checked 9 Nov 2026. Scarborough P., Clark M., Cobiac L., et al. (2023), “Vegans, vegetarians, fish-eaters and meat-eaters in the UK show discrepant environmental impacts”, Nature Food 4: 565–574 — Table 3 (GHG, GWP100) and Table 4 (land use, water use, eutrophication), medians standardised to 2,000 kcal.

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