Methodology
How we estimate CO₂e and what the numbers mean.
Overview
This calculator estimates the carbon dioxide equivalent (CO₂e) emissions associated with different dietary patterns and the potential emissions savings from switching diets over time.
Estimates are based on average daily dietary carbon footprints reported in a peer-reviewed study that analyzed food diaries from adults following different diets. The results are intended for educational and comparative purposes, not as precise measurements of individual environmental impact.
Data source
Emission values are derived from a 2024 peer-reviewed study that analyzed 7-day food diaries collected from Polish adults across four dietary groups:
- •Vegan
- •Vegetarian
- •Fish-eater (pescatarian)
- •Meat-eater
Participants recorded foods and beverages consumed, including portion sizes. Dietary carbon footprints were calculated using standardized CO₂-equivalent emission factors from publicly available databases.
Diet definitions
The dietary groups used in this calculator follow the definitions applied in the underlying peer-reviewed study. Participants were classified based on their reported food intake over a 7-day period.
Meat-eater
Diets that include meat from land animals (such as beef, pork, poultry, or processed meat), and may also include fish, dairy products, eggs, and plant-based foods.
Fish-eater (pescatarian)
Diets that exclude meat from land animals but include fish or seafood. Dairy products, eggs, and plant-based foods may also be consumed.
Vegetarian
Diets that exclude meat and fish but include animal-derived products such as dairy and eggs, alongside plant-based foods.
Vegan
Diets that exclude all foods of animal origin, including meat, fish, dairy products, and eggs. Only plant-based foods are consumed.
These definitions are based on dietary classifications used in Mazur et al. (2024) and are intended for comparative analysis rather than strict dietary labeling.
Emission factors used
The calculator uses the mean daily dietary carbon footprint reported for each dietary group:
| Diet type | Mean daily footprint (kg CO₂e / day) |
|---|---|
| Meat-eater | 3.62 |
| Fish-eater | 2.72 |
| Vegetarian | 2.45 |
| Vegan | 1.38 |
These values represent population averages and include emissions associated with food production and consumption patterns observed in the study.
Calculation method
- 1 Select a baseline diet and a new diet
- 2 Multiply each diet’s average daily footprint by the selected number of days
- 3 Calculate emissions savings as the difference between the two totals
Formula
CO₂ saved = (baseline daily footprint − new daily footprint) × number of days
Results are presented in kilograms of CO₂e and as a percentage reduction relative to the baseline diet.
Interpretation and limitations
- •Results are estimates, not exact personal measurements
- •Data reflects dietary patterns observed in one country and may vary across regions
- •Individual food choices, calorie intake, and sourcing are not explicitly modeled
- •The study is observational, not causal
Despite these limitations, the calculator provides a useful comparison of how different dietary patterns generally relate to carbon emissions.
Intended use
This tool is designed to:
- •Illustrate relative differences between dietary patterns
- •Support climate education and awareness
- •Encourage reflection on food-related environmental impact