---
term: "Emission factor"
aliases: ["EF", "characterisation factor", "GHG emission factor"]
category: Concept
updated: 2026-09-08
canonical: https://verdatir.com/glossary/emission-factor
publisher: Verdatir (https://verdatir.com)
---

# Emission factor

> A coefficient that converts a quantity of activity, such as a kilowatt-hour of electricity or a kilogram of steel, into an estimated quantity of greenhouse gas emissions or other environmental impact.

Emission factors are the multipliers at the heart of every carbon footprint and life cycle inventory. Activity data, such as tonnes of material purchased or litres of fuel burned, are multiplied by an emission factor to estimate emissions.

## Sources

Emission factors come from life cycle inventory databases such as ecoinvent, from national inventories and government publications, from industry associations, and increasingly from suppliers themselves in the form of supplier-specific product carbon footprints. Each source carries its own boundary, geography, technology mix and reference year.

## Why they need checking

An emission factor is only valid for the activity, region and period it describes. Applying a European grid factor to a factory in Southeast Asia, or a 2015 factor to 2026 production, changes the result materially. In large reports, factor selection errors are common, quiet and hard to find by sampling.

## Characterisation factors

In a full LCA, characterisation factors perform a similar role at the impact assessment stage, converting inventory flows into impact category indicators such as kg CO2e or kg SO2e.

## Where Verdatir fits

Verdatir cross-checks the emission factors in a submission against their stated source, region and vintage, and flags factors that do not match the activity they are applied to.

## Sources

- [GHG Protocol — Calculation tools and guidance](https://ghgprotocol.org/calculation-tools-and-guidance)