Diet Carbon Footprint Calculator
The greenhouse gas emissions of a diet over a year, and how much changing it would save — using the per-diet figures from the Scarborough study.
Food accounts for roughly a quarter of global greenhouse gas emissions, and within food the spread between diets is large.
How the diet carbon footprint calculator works
Food accounts for roughly a quarter of global greenhouse gas emissions, and within food the spread between diets is large. The figures here come from Scarborough et al. (2014), which measured the diets of 55,000 people in the UK and reported daily emissions by dietary group: about 7.2 kg CO₂e a day for high meat-eaters down to 2.9 kg for vegans.
The dominant factor is ruminant meat. Beef and lamb emit roughly ten times as much per gram of protein as chicken or pork, because of methane from digestion and the land required. That is why the gap between a high-meat and a low-meat diet is much larger than between a low-meat and a vegetarian one.
Formula: annual emissions = daily figure for the diet × 365.25
Worked examples
| Inputs | Emissions per year | Note |
|---|---|---|
| A medium-meat diet | 2.06 tonnes | 2.06 tonnes a year |
| High meat against vegan | 2.63 tonnes | 1.57 tonnes more a year |
| A household of four, vegetarian | 5.57 tonnes | 5.57 tonnes against 10.5 |
FAQFrequently asked questions
How much CO₂ does my diet produce?
Between about 1.05 tonnes a year for a vegan diet and 2.63 tonnes for a high-meat one, on the Scarborough figures.
Why is beef so much worse?
Ruminants produce methane as they digest, and beef needs far more land per gram of protein. Beef and lamb emit roughly ten times as much as chicken or pork.
Is going vegetarian much better than eating less meat?
The big step is cutting ruminant meat. Low-meat and vegetarian diets are close together; both are well below high-meat.
How reliable are these figures?
The ranking is robust and repeatedly replicated. The absolute numbers vary by country, season and supply chain, so treat them as comparisons.
Does local food help?
Less than most people expect. Transport is a small share of food emissions for most products — what you eat matters far more than how far it travelled.
Where these figures come from
- UK DESNZ / DEFRA — Greenhouse gas reporting: conversion factors — the flight, fuel and waste emission factors used here
- Scarborough et al. (2014), Climatic Change — Dietary greenhouse gas emissions — the per-diet daily emission figures
- US EPA — Technical Assistance Document for the Reporting of Daily Air Quality (AQI) — the PM2.5 breakpoints the air quality calculator uses
- US EPA — Greenhouse Gas Equivalencies Calculator — the official US equivalency factors
Last checked: September 2026. Factors are taken from published government and peer-reviewed sources, each named on the page with its year.