- An emission factor converts an activity data point (kWh, liter, km, euro) into CO2e emissions.
- The French public reference is the ADEME Base Empreinte, free of charge; it succeeded the Base Carbone.
- Physical factors are precise but data-hungry; monetary factors are fast but less precise.
- Best practice: keep a consistent, documented source for each category, and record the factor version from one year to the next.
What is an emission factor?
An emission factor is a coefficient that converts an activity into greenhouse gases. It answers a simple question: how much CO2e does one unit of a given activity generate. Multiplied by your activity data, it gives your emissions:
emissions (tCO2e) = activity data × emission factor.
It is the building block of every calculation, whatever the method. You use it at each step of the carbon footprint calculation, on each of the scopes 1, 2 and 3.
Which unit does an emission factor use?
An emission factor is always expressed as a mass of CO2e per unit of activity: kg CO2e per kilowatt-hour, kg CO2e per liter, kg CO2e per kilometer, or kg CO2e per euro spent. CO2e (CO2 equivalent) converts every greenhouse gas to a common measure, weighting each one by its warming power.
For example, a factor of 0.2 kg CO2e per kWh applied to 10,000 kWh consumed gives 2,000 kg, or 2 metric tons of CO2e for that category.
Where do you find the official emission factors?
In the ADEME Base Empreinte. It is the official public database of the emission factors and inventory datasets needed for organizations' carbon accounting and for the environmental labeling of products. It is free and open to everyone, and it is the reference for the French regulatory footprint.
For specific categories, other databases complement the Base Empreinte. Agribalyse, the ADEME database dedicated to agricultural and food products, provides detailed factors for that sector, based on life cycle assessment. Ecoinvent, an international life cycle assessment database under paid license, covers more than 26,000 sector datasets and helps when you need fine granularity or categories outside France's coverage. Companies often add the data suppliers send directly for their own products.
ADEME documents and updates its factors, and publishes sector studies to refine the precision of some of them. The rule remains to keep a consistent, documented source for each category, and to keep it from one year to the next so that your variations reflect real changes, not a change of source.
What is the difference between Base Carbone and Base Empreinte?
The Base Empreinte succeeded the Base Carbone. Historically, ADEME published emission factors through the Base Carbone. The Base Empreinte now gathers, in a single portal, those emission factors (for organizations' carbon accounting) and the life cycle assessment data (for the environmental labeling of products). When an older source mentions the "Base Carbone", it refers to the same factors, today accessible through the Base Empreinte.
Physical or monetary factors: which one to choose?
Both, depending on the data you have. The physical factor (per kWh, per km, per kg) is precise but requires detailed, reliable data. The monetary factor (per euro spent) is less precise, because it averages very different realities, but it lets you cover a broad range quickly when the physical data is missing, particularly on purchases.
Common practice: start with monetary factors to map every category and spot the heaviest ones, then refine those priority categories with physical factors. There is no point chasing physical precision on a category that matters little. That choice mainly plays out on scope 3, the most dependent on supplier data.
Use the right factors with Ditto
The calculation is simple; the hard part is elsewhere, in choosing the right factor for each category and in staying consistent from one cycle to the next. Ditto integrates Base Empreinte factors, applies them automatically to your activity data, keeps track of the versions used and spots the categories to refine. A dedicated coach teaches you the method so you can run it yourself in the next cycle. And for a first calculation, a platform like Ditto saves time, but the Base Empreinte and a well-kept spreadsheet already take you a long way.
Convert your data without picking the wrong factor
A Ditto expert shows you how to choose and apply the right emission factors to your categories.
Emission factors: key takeaways
| Element | Summary |
|---|---|
| Definition | Coefficient that converts an activity data point into CO2e |
| Unit | Mass of CO2e per unit (kWh, liter, km, euro) |
| Official French source | ADEME Base Empreinte, public and free |
| Base Carbone | Former name, factors now published through the Base Empreinte |
| Physical vs monetary | Physical = precise; monetary = fast; start monetary, refine with physical |
| Other databases | Agribalyse (food, ADEME), Ecoinvent (international, licensed), supplier data |
Frequently asked questions
What is an emission factor?
A coefficient that converts an activity into greenhouse gas emissions. Multiplied by your activity data (kWh, liter, km, euro), it gives your emissions in CO2e. It is the basis of every carbon footprint calculation.
Where do you find the ADEME emission factors?
In the Base Empreinte (base-empreinte.ademe.fr), the official public database of emission factors and inventory datasets. It is free and is the reference for organizations' carbon accounting in France. For specific categories, other databases complement it, such as Agribalyse (food) or Ecoinvent (international, licensed). Those product databases are used in particular for life cycle assessments, which we cover in our article on life cycle assessment and product carbon footprint.
Are emission factors public?
Yes. The ADEME Base Empreinte is public and freely accessible. That is what allows any company to calculate a first footprint without buying a database.
What is the difference between a physical and a monetary factor?
The physical factor (per kWh, km, kg) is precise but requires detailed data. The monetary factor (per euro spent) is less precise but quick to apply when the physical data is missing. Companies often start with monetary factors, then refine the heaviest categories with physical ones.
