Carbon footprint: what it is and how to calculate it

A carbon footprint is the total amount of greenhouse gases (GHG) released into the atmosphere, directly or indirectly, by a person, organisation, product or event over a defined period, usually one year. It is expressed in tonnes of CO₂ equivalent (CO₂e), a unit that brings different gases together into a single comparable figure.

Measuring your carbon footprint is the first step towards cutting emissions: what cannot be measured cannot be managed.

What is a carbon footprint?

The carbon footprint quantifies the impact an activity has on the climate through the GHG emissions it causes. It is not limited to carbon dioxide: it accounts for every greenhouse gas, weighted by its capacity to warm the atmosphere, and translates them into a single figure in CO₂ equivalent.

These gases are essential to life because they regulate the planet's temperature through the greenhouse effect. The problem is excess: the rising concentration of human-made GHG intensifies global warming and climate change.

Why is it important to measure your carbon footprint?

More than a calculation, the carbon footprint is a management tool. Measuring it lets you:

• Understand your real impact: identify and quantify emission sources, separating direct emissions (combustion in your own facilities or vehicles) from indirect ones (purchased electricity, supply chain, business travel).
• Set a baseline: establish a starting point against which to track the progress of any reduction strategy.
• Prioritise where to act: concentrate effort on the processes that emit the most, where reductions are most cost-effective.
• Comply with regulation: a growing number of rules, such as the EU's CSRD or Spain's MITECO carbon-footprint registry, require companies to measure and report emissions.
• Strengthen reputation: customers, investors and public tenders increasingly value credible, verifiable climate management.

Which gases does the carbon footprint include?

The Kyoto Protocol recognises seven greenhouse gases, and any of them can form part of a carbon footprint:

• Carbon dioxide (CO₂): the most abundant, linked to burning fossil fuels.
• Methane (CH₄): from livestock, landfills and waste management.
• Nitrous oxide (N₂O): associated with fertilisers and agricultural and industrial processes.
• Hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs): used in refrigeration and industrial processes.
• Sulphur hexafluoride (SF₆) and nitrogen trifluoride (NF₃): used in electrical equipment and electronics.

Each gas has a different global warming potential (GWP), which measures how much heat it traps compared with CO₂ over a 100-year horizon. Applying the GWP, all emissions are converted into a common unit: CO₂ equivalent. Methane, for example, has a far higher GWP than CO₂, so a small leak weighs heavily on the final result.

Types of carbon footprint

It helps to distinguish four approaches according to what is being measured:

1. Personal carbon footprint

Captures the emissions of a person's everyday activities: home energy use, mobility, food and waste.

2. Product carbon footprint

Assesses the impact of a product across its entire life cycle, from raw material extraction to end of life. It is the basis of the product carbon footprint (PCF), governed by standards such as ISO 14067.

3. Event carbon footprint

Measures the impact of conferences, festivals or competitions, where attendee travel, energy use and waste generate significant emissions. This is the event carbon footprint.

4. Corporate carbon footprint

Measures the emissions of a company's entire activity. To organise them, the GHG Protocol classifies emissions into three scopes:

Scope 3 usually represents the largest share of the corporate footprint and is also the hardest to measure, because it depends on supplier data. You can go deeper into the difference between scope 1, 2 and 3 emissions and the 15 categories of scope 3.

How is a carbon footprint calculated?

The calculation rests on two international references that are best combined: the GHG Protocol, the most widely used methodological framework in the world, and the ISO 14064-1:2018 standard, which is certifiable and aligned with regulation. You can see a detailed comparison in our guide on GHG Protocol vs ISO 14064-1.

Whatever the type of footprint, the process follows these steps:

1. Define the scope and boundaries: decide which activities, facilities and scopes (1, 2 and 3) enter the calculation and which period is analysed.
2. Collect activity data: gather fuel and electricity consumption, distances travelled, waste generated, purchases, and so on.
3. Apply emission factors: convert each piece of activity data into emissions using official, up-to-date emission factors.
4. Calculate in CO₂ equivalent: add up all the gases weighted by their GWP to obtain the total in tonnes of CO₂e.
5. Analyse the results: identify emission hotspots and set the baseline.
6. Reduce and monitor: define a reduction plan and repeat the measurement each year to verify progress.

ISO 14064-1:2018 organises emissions into six reporting categories (direct emissions; indirect emissions from imported energy; from transport; from products used by the organisation; associated with the use of products; and other indirect emissions), an approach compatible with the three scopes of the GHG Protocol.

Tools to calculate and manage your carbon footprint

Calculating a carbon footprint by hand becomes complex in companies with many sites and suppliers. Specialised software automates the process and reduces the risk of error.

The Manglai platform, built on the GHG Protocol and ISO 14064, lets you:

• Automate data collection through integration with ERP systems, utility invoices and fleet management tools.
• Calculate emissions across all three scopes with up-to-date emission factors.
• Visualise and analyse the results in dashboards and auditable reports.
• Simulate reduction scenarios and plan decarbonisation actions.
• Prepare reporting for the CSRD or the MITECO carbon-footprint registry.

Frequently asked questions about the carbon footprint

In what unit is the carbon footprint measured?

In tonnes or kilograms of CO₂ equivalent (CO₂e), a unit that groups all greenhouse gases weighted by their global warming potential.

What is the difference between a carbon footprint and climate neutrality?

The carbon footprint measures emissions; climate neutrality is reached when those emissions are cut as far as possible and the remainder is offset, so that the net balance is zero.

Are companies required to calculate their carbon footprint?

It depends on their size and sector. In the EU, the CSRD requires a growing number of companies to report emissions, and in Spain the MITECO carbon-footprint registry is mandatory for certain large companies. Many SMEs also calculate it because their customers demand it across the supply chain.

The first step is always to measure. You can start with our free carbon footprint calculator or see how Manglai automates calculation and reporting with its carbon footprint solution.