How to Calculate Scope 3 Emissions: A Step-by-Step Guide

Dive into the methodology behind Scope 3 emissions calculations. This guide offers a clear roadmap, ensuring you capture every carbon footprint detail in your supply chain."

How to Calculate Scope 3 Emissions: A Step-by-Step Guide
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Scope 3 emissions, encompassing all indirect emissions in a company's value chain, can be complex to quantify. However, understanding and measuring these emissions is crucial for any comprehensive sustainability strategy. In this guide, we'll walk you through the steps to accurately calculate Scope 3 emissions.

1. Identify Relevant Categories:

The Greenhouse Gas Protocol identifies 15 categories of Scope 3 emissions. Start by determining which categories are relevant to your organization. These might include purchased goods and services, capital goods, fuel- and energy-related activities, and more.

2. Gather Data:

Collect data on each relevant category. This might involve:

  • Surveying suppliers for their emissions data.
  • Analyzing purchase records to determine quantities of goods or services bought.
  • Using industry averages if specific data isn't available.

3. Choose Emission Factors:

Emission factors convert activity data (like the number of miles driven or tons of waste disposed) into carbon equivalents. Use recognized databases like the UK's DEFRA or the US EPA's eGRID to find appropriate factors.

4. Perform Calculations:

Multiply your activity data by the relevant emission factors. For instance, if you're calculating emissions from business travel, you'd multiply the number of miles flown by the emission factor for air travel.

5. Consider Double Counting:

Be wary of double-counting emissions, especially if you're also calculating Scope 1 and 2 emissions. For instance, emissions from company-owned vehicles would fall under Scope 1, not Scope 3.

6. Use Specialized Software:

There are several software tools available that can simplify the process of calculating Scope 3 emissions, especially for large organizations with complex supply chains.

7. Regularly Update and Refine:

Emission factors, organizational activities, and the availability of data can change over time. Regularly review and update your calculations to ensure they remain accurate.


While calculating Scope 3 emissions can be a complex task, it's an essential component of understanding a company's full environmental impact. By following this step-by-step guide, organizations can gain a clearer picture of their indirect emissions and identify opportunities for reduction.

Looking for more insights on sustainability and emissions? Dive deeper with our Scope 3 Foundations Series for comprehensive guides and expert insights.