CO2e Meaning: Definition, Calculation and Examples

What does CO2e mean?

CO2e means carbon dioxide equivalent. It is the amount of CO2 that would trap the same heat as a given amount of another greenhouse gas over a set time.

Companies emit a mix of gases: carbon dioxide from fuel, methane from livestock and landfill, nitrous oxide from fertiliser, and fluorinated gases from refrigerants. Each gas traps a different amount of heat. CO2e puts them all on one scale, so a business can report a single footprint, set one target and compare sites, products and suppliers.

You will see it written as CO2e, CO2eq or CO2-e. They all mean the same thing. Footprints are usually reported in tonnes, written tCO2e.

Which greenhouse gases does CO2e cover?

CO2e covers the seven gases in the GHG Protocol Corporate Standard. These are the six from the Kyoto Protocol, plus nitrogen trifluoride (NF3), which was added under the Kyoto Protocol's Doha Amendment in 2012.

Carbon dioxide is the largest share by far. The EU's EDGAR database puts 2024 global emissions at about 53.2 GtCO2e, excluding land use. Of that, fossil CO2 was about 74.5%, methane about 17.9%, nitrous oxide about 4.8% and F-gases about 2.8% (EDGAR 2025 report, JRC, September 2025).

What is the difference between CO2 and CO2e?

CO2 is one gas. CO2e is a unit that can describe all greenhouse gases together.

"1,000 tonnes of CO2" counts only carbon dioxide. "1,000 tCO2e" could be a mix of CO2, methane and other gases that adds up to the same warming as 1,000 tonnes of CO2. A footprint reported only in CO2 leaves out methane, nitrous oxide and F-gases. For farms, food companies and anything with refrigeration, that gap can be large.

What is global warming potential (GWP)?

GWP measures how much heat one tonne of a gas traps over a set period, compared with one tonne of CO2. CO2 has a GWP of 1 by definition.

Most reporting uses the 100-year GWP (GWP100). Values come from the Intergovernmental Panel on Climate Change (IPCC) and are revised with each assessment report. The table below shows the values from the Fifth Assessment Report (AR5, 2014) and the Sixth (AR6, 2021).

Sources: IPCC AR6 WGI, Chapter 7 (2021); IPCC AR5 WGI (2014).

Use one set of GWPs consistently across your inventory and say which one you used. The GHG Protocol asks companies to use 100-year values from the IPCC, and most now use AR6. Changing GWP set changes your numbers, so if you switch, recalculate your base year.

How do you calculate CO2e?

Multiply the mass of each gas by its GWP, then add up the results.

CO2e = Σ (mass of gas × GWP of that gas)

In practice, most companies don't measure gas directly. They multiply activity data (litres of diesel, kWh of electricity, tonnes of fertiliser, dollars spent) by an emission factor that is already expressed in CO2e. Our guide to calculating GHG emissions covers emission factors and data step by step.

Worked example: a food processing site

Say a site's annual records show these emissions. The numbers are made up to show the method. They are not real data.

CO2 is 54% of this footprint. The other 46% comes from gases that make up only 11.2 tonnes of the mass. If the site reported only CO2, it would miss almost half of its warming impact. The refrigerant leak alone outweighs the methane, which is why chiller maintenance often appears early in decarbonisation plans.

How are CO2e figures used?

CO2e is the unit for almost every climate number a business reports, buys or pays for.

• Corporate footprints and targets. Scope 1, 2 and 3 inventories under the GHG Protocol are reported in tCO2e, and the Science Based Targets initiative (SBTi) sets targets in the same unit. See all about GHG scope categories.
• Climate disclosure. Rules such as IFRS S2, AASB S2 and California's SB 253 ask for gross Scope 1, 2 and 3 emissions in tCO2e.
• Carbon pricing. Carbon taxes and emissions trading systems charge per tonne of CO2e covered. Read more in carbon pricing and CO2e.
• Product footprints. A product carbon footprint gives kgCO2e per unit, so buyers can compare products.

What are everyday examples of CO2e?

Everyday activities create CO2e through energy, fuel and materials. How much depends on the emission factor for that activity in that place.

For company reporting, use emission factors from a named, dated source, such as your national government's conversion factors or the IEA. Don't use rules of thumb.

Terrascope customer example: CO2e at product level

Pokka needed CO2e footprints for a whole product range, not one or two hero products. With Terrascope, Pokka calculated product carbon footprints for 4,980 SKUs, at about 92% accuracy across the 700 SKUs that were checked. Read the Pokka case study.

How Terrascope helps

Terrascope turns your activity data into CO2e across Scope 1, 2 and 3, using one GWP set and dated emission factors, so every number can be traced and audited.

• Corporate footprint: the Terrascope carbon footprint platform brings in energy, fuel, refrigerant, spend and supplier data, applies emission factors and shows CO2e by gas, scope, site and business unit.
• Product footprints: the product carbon footprint module calculates kgCO2e per SKU at scale.
• Business case: use the carbon management ROI calculator to estimate the time and cost of moving off spreadsheets.

Want to see your own footprint in CO2e, broken down by gas and source? Talk to our team.

FAQs

What does CO2e stand for?

CO2e stands for carbon dioxide equivalent. It expresses the warming effect of any greenhouse gas, or a mix of gases, as the amount of CO2 that would cause the same warming over a set period, usually 100 years.

Is CO2e the same as carbon emissions?

Not quite. "Carbon emissions" often means CO2 only. CO2e includes CO2, methane, nitrous oxide and fluorinated gases, each weighted by its global warming potential. Most corporate reporting rules ask for CO2e.

How do I convert methane to CO2e?

Multiply the tonnes of methane by its GWP. With IPCC AR6 100-year values, use 27.0 for non-fossil methane (livestock, landfill) or 29.8 for fossil methane. So 10 tonnes of non-fossil methane is 270 tCO2e.

Which GWP values should I use, AR5 or AR6?

Use the values your reporting framework or regulator requires. Where you have a choice, most companies now use IPCC AR6 100-year values. Whichever you pick, use it across the whole inventory, state it in your report and recalculate your base year if you change.

What is the difference between tCO2e and MtCO2e?

They are the same unit at different scales. One tCO2e is one tonne of carbon dioxide equivalent. One MtCO2e is one million tonnes, and one GtCO2e is one billion tonnes, which is the scale used for national and global totals.

Why do companies report in CO2e instead of each gas?

One unit lets companies add, compare and set targets across all gases. Most disclosure rules also ask for gas-by-gas detail for Scope 1, so good systems keep both: the gas-level data and the CO2e total.