Introducing the New GZA Scope 3 Calculator!

Our goal is to remove the barriers organizations face in addressing their climate change impact. With that goal in mind, we built our Scope 3 Calculator as simple to use, affordable, and easy to deploy by organizations at any scale without specialized training.


The need for quantification and disclosure of Scope 3 emissions continues to escalate, and to help organizations meet this complex challenge, GZA is proud to release our latest version of the GZA Scope 3 Calculator.

This Calculator enables users to evaluate and assess the Greenhouse Gas (GHG) Emissions from their supply chain, also known as Upstream Scope 3 Emissions. The Calculator can serve as a fundamental first step in your organization’s Scope 3 journey. We have applied the emissions factors from United States Environmentally-Extended Input-Output (USEEIO) models, and integrated numerous updates to help users understand, apply, and view results from those factors.  

Anyone is welcome to download a limited free version of the Scope 3 Calculator. If you would like to use the Full Version of the GZA Scope 3 Calculator, with all of the features listed below, it is available for purchase. Please scroll below for more details.

How can the GZA Scope 3 Calculator help your organization?

Instant Upstream Scope 3 results

Enter your organization’s supply chain spend – disaggregated by supplier, purchasing category, or other commodity-specific category – and as you assign an Industry or Commodity to each entry, the Calculator will automatically assign the related USEEIO emissions factor to that entry. Based on the user-selected year, the emissions factors are automatically adjusted for United States currency inflation rates and the decarbonization of the US electric grid. With the Full Version of the Calculator, users can enter up to 2,000 unique entries to be compiled in your total Upstream Scope 3 results.

View your emissions factors at a greater level of detail

We understand that EEIO factors can be difficult to visualize or understand for users new to Scope 3. So instead of hiding the factors in background calculations, the GZA Scope 3 Calculator transparently presents the emissions factors for each selectable Commodity, broken down at different levels of your organization’s supply chain. The factors for 2012 (the source year of the USEEIO model) are also presented alongside the adjusted factors for the user-selected year to show the estimated impact of currency inflation and electric grid decarbonization. Even with over 400 Commodities to choose from, we know that in many cases it can be difficult for users to determine which emissions factor is most relevant to the good or service being evaluated. That is why the Calculator also provides a list of over 19,000 items or services across over 970 NAICS Titles, aligned to the USEEIO Industries and Commodities.

Scope 3 Summaries, Hotspots, and Charts – Automatically Generated

The Calculator gives your organization instant insights into your Scope 3 emissions through a variety of functions and features: 

  • Automated summaries of your supply chain’s GHG emissions, sorted by their upstream Scope 3 category 
  • Hotspot analyses of Scope 3 emissions, sorted by user-defined suppliers and categories 
  • Major industry groups where emissions are occurring in your supply chain
  • Resources and links to Scope 3 guidance  
  • Recommendations to help your organization continue to address its Scope 3 impact

Download the free version of the Calculator to apply the features and resources available!

Perform high-level emissions forecasts to plan your Scope 3 emissions

Once you have completed your organization’s Upstream Scope 3 emissions inventory in the Calculator, you can then take your Scope 3 Results to the next level by using our custom Forecasting Tool. Using the results within the Calculator as a Baseline, you can then set an absolute reduction target and modify a variety of high-level variables to better understand what supply chain-level actions would be required to meet the target.


Frequently Asked Questions

What is included with the purchase of the GZA Scope 3 Calculator? How much does it cost?

Users can purchase the GZA Scope 3 Calculator for $2,500 USD. Once the purchase is completed, users will be provided the Calculator (in the format of a Microsoft Excel workbook). 

What software does the GZA Scope 3 Calculator use?

The GZA Scope 3 Calculator is a Microsoft Excel-based tool. It employs Visual Basic Macros to create a simplified and user-friendly experience, all within Excel. Scope 3 calculations can also comprise of hundreds, even thousands, of unique spend data points that are commonly available in CSV or Excel format. Formatting and transferring this spend data into an Excel-based tool simplifies the Scope 3 calculation process, as opposed to having to manually enter or upload each spend data point via an online platform.

Do I need to be connected to the internet to use the Scope 3 Calculator? Will I be required to share my data with any external party?

There are no connections to external databases and no required internet connections or data sharing. Once you have downloaded the Calculator, you are able to use it completely offline, on your computer and/or your organization’s network. 

As these Scope 3 calculations can require confidential supply chain spend data, this gives our users full control of their data security. 

What type of information is required to use the Calculator?

The Calculator requires users to enter their spend. This Calculator applies the US Environmentally-Extended Input-Output (USEEIO) v2.0.1-411 model which correlates spend with the associated environmental impacts of an industry (the producer). Thus, users are required to enter their organization’s spend (in USD) on goods and services (i.e., spend with their suppliers).

What is USEEIO?

The US Environmentally-Extended Input-Output (USEEIO) model is a publicly-available, environmentally-extended input-output model of the United States, released by the US Environmental Protection Agency (EPA). The USEEIO model referenced in the GZA Scope 3 Calculator (USEEIO v2.0.1-411) creates a life cycle model of 411 US goods and services by combining economic transaction data between the 411 industry sectors with each sector's environmental data spanning land impacts, water impacts, mineral usage, nutrients and toxics, criteria air pollutants, energy, and greenhouse gas emissions. The USEEIO v2.0.1-411 model provides life cycle results per $1 (in 2012 USD) demand for all goods and services in the model in the producer's price and purchaser's price.

Can the results of the GZA Scope 3 Calculator be used in my organization's external reporting?

Users must consider the reporting criteria of their disclosure platforms before using any information or following any of the recommendations provided by the GZA Scope 3 Calculator. Users must also understand the inherent uncertainty in emissions results when using spend-based Environmentally-Extended Input-Output (EEIO) factors, compared to quantifying emissions using product-level life cycle factors or via collecting emissions data directly from suppliers. The use of EEIO factors is an accepted Scope 3 calculation methodology in the GHG Protocol, and can be used to establish emissions baselines for Scope 3 emissions targets. This methodology should be used as an initial step in an organization’s Scope 3 strategy. The Calculator can help your organization identify the biggest contributors to your upstream Scope 3, after which you are then encouraged to address those significant emissions sources via more accurate calculation methodologies which enable actionable emissions reduction actions.

Can the GZA Scope 3 Calculator support an organization’s submission to the Science-Based Targets initiative (SBTi)?

Use of the GZA Scope 3 Calculator is an acceptable pathway for both conducting a Scope 3 screening and creating a Scope 3 Inventory for submission to SBTi, as it uses activity data and methods outlined in the GHG Protocol. However, users should be aware of several factors and limitations as they proceed with use of the GZA Calculator (or any spend-based calculation methods):

Scope 3 Emissions Screening

Per the SBTi Criteria as of 10/04/2023, “Companies must complete a scope 3 inventory covering gross scope 3 emissions for all its emissions sources according to the minimum boundary of each scope 3 category set out by the GHG Protocol Corporate Value Chain (Scope 3) Accounting and Reporting Standard.”

The GZA Scope 3 Calculator can assist with screening (estimating / calculating) emissions primarily for upstream Scope 3 categories 1 through 6, and 8, if your company is able to compile and enter the associated spend related to each category. For employee commute emissions (Category 7) and downstream Scope 3 Categories ( e.g., use of sold products, end-of-life treatment of sold products, investments, etc.), your company will have to use other estimation methods to determine the potential magnitude of emissions in these categories.

This may seem like a huge calculation ordeal, we can offer some overall perspective to provide some relief:

  • Companies in the manufacturing or service sector often find a majority of their scope 3 emissions occur in upstream supplier activities (which our Calculator covers). If these companies produce products that use energy or emit greenhouse gases (e.g., engines, cars, appliances), then the use of these products is most likely another large scope 3 source.
  • Companies in the transportation sector also often find that their Scope 3 is also primarily concentrated in their upstream supplier activities, though downstream scope 3 from additional logistics activities might be significant depending on how the company operates.

Once the screening effort is complete, if a company’s relevant scope 3 emissions are 40% or more of total scope 1, 2, and 3 emissions, they must be included in Near Term science-based targets. However, if your company is also setting long-term science-based targets, then all relevant scope 3 categories must be included (90% of Scope 3).

Scope 3 Emissions Coverage

For Near-Term science-based targets, two-thirds of your company’s scope 3 emissions must be included in the target. We recommend that you choose the parts of scope 3 emissions that are most relevant to your company and where your company has the best ability to engage with and improve the accuracy of Scope 3 calculations. And for Long-Term science-based targets, 90% of your company’s scope 3 emissions must be included in the target.

If your company’s Scope 3 target includes baseline results that were produced in the GZA Scope 3 Calculator, and assuming that your data entries in the Calculator are provided at the supplier-level or the product-level, then you will have a reasonable understanding of which of your suppliers and products contribute the most to your Scope 3 emissions. That said, the GZA Scope 3 Calculator uses spend-based industry-averaged emissions factors, which are not updated annually and whose reductions over time can only reflect the average decarbonization of the US economy.

So while the GZA Scope 3 Calculator can help your company set a Scope 3 target and develop a target baseline, to show progress against your target your company will need to pursue more accurate emissions data (e.g., supplier surveys, supplier commitments to GHG targets, life cycle assessment of products, etc.) which you can then “swap out” with future emissions results of the GZA Scope 3 Calculator to show reductions over time.

The limitations and processes we have outlined above are inherent to any spend-based Scope 3 calculation methodology, and are a key step in an organization’s journey to calculating Scope 3 and setting an emissions reduction target.