Carbon Footprint Formula
Calculate CO2 emissions from energy use, travel, and consumption.
Learn the key formulas for estimating your carbon footprint.
The Core Formula
A carbon footprint measures the total greenhouse gas emissions caused by an individual, event, organization, or product. It is expressed in equivalent tons of CO₂ (tCO₂e).
Variables
| Symbol | Meaning |
|---|---|
| Activity Data | Quantity consumed (kWh, liters, miles, etc.) |
| Emission Factor | CO₂ produced per unit of activity (kg CO₂/unit) |
| tCO₂e | Tonnes of CO₂ equivalent |
Common Emission Factors
| Activity | Emission Factor |
|---|---|
| Electricity (US average) | 0.42 kg CO₂/kWh |
| Natural gas | 2.0 kg CO₂/m³ |
| Gasoline / petrol | 2.31 kg CO₂/liter (8.75 kg CO₂/gallon) |
| Diesel | 2.68 kg CO₂/liter (10.15 kg CO₂/gallon) |
| Short-haul flight | 0.255 kg CO₂/km per passenger |
| Long-haul flight | 0.195 kg CO₂/km per passenger |
Example 1 — Electricity
A household uses 900 kWh of electricity per month (US average). What are the monthly CO₂ emissions?
CO₂ = Activity × Emission Factor
CO₂ = 900 kWh × 0.42 kg/kWh
CO₂ = 378 kg (0.378 tonnes) per month
Example 2 — Driving
A car uses 50 liters of gasoline per week. What are the weekly CO₂ emissions?
CO₂ = 50 liters × 2.31 kg/liter
CO₂ = 115.5 kg per week (about 6 tonnes per year)
Example 3 — Flying
A round-trip flight from New York to London is approximately 11,200 km total. What are the emissions for one passenger?
CO₂ = 11,200 km × 0.195 kg/km (long-haul factor)
CO₂ ≈ 2,184 kg (2.18 tonnes) per passenger
Global Averages
| Country/Region | Annual Per Capita (tCO₂) |
|---|---|
| United States | ~15.5 |
| European Union | ~6.8 |
| China | ~8.0 |
| India | ~1.9 |
| World average | ~4.7 |
When to Use It
- Estimating personal or household carbon footprint
- Corporate sustainability reporting
- Comparing environmental impact of different transportation choices
- Setting and tracking emission reduction goals