Spend-Based vs Activity-Based Emissions for Events: Which Method Should You Use?
Measuring the carbon footprint of an event can feel like another big task when you're already managing venue bookings, catering, suppliers, registrations and everything else involved in bringing an event together.
You might have detailed information about attendee travel, electricity consumption and production materials. Or perhaps you're working with invoices, budgets and purchasing records, without having access to all the physical data behind those purchases.
If you're looking for quick event carbon tracking, you may be wondering whether you need to collect every piece of information before you can get started.
There are different ways to calculate event emissions, and the most suitable approach depends on the information available and what you need the results for.
Two of the most common approaches are spend-based and activity-based emissions calculations. Both can help you understand the greenhouse gas emissions associated with your event, but they use different types of data.
Spend-based carbon accounting uses financial expenditure, while activity-based carbon accounting uses information about physical activities, such as travel distances, energy consumption and material quantities.
For university events departments, small businesses and busy event organisers, understanding the difference can make carbon tracking more manageable.
In this guide, we'll compare both approaches, explain how to estimate event carbon emissions when information is limited, and explore how Scope Carbon Tracking supports different calculation methods across its event software.
Spend-Based vs Activity-Based Emissions: What's the Difference?
The main difference between spend-based vs activity-based emissions calculations is the information used to estimate greenhouse gas emissions.
Spend-based emissions use financial expenditure and monetary emission factors. For example, the cost of purchased event materials.
Activity-based emissions use physical quantities and activity-based emission factors. For example, electricity consumed, kilometres travelled or kilograms of materials purchased.
Spend-based methods can be quicker when invoices and purchasing records are already available.
Activity-based methods can provide more specific information about event activities when reliable data is available.
Both approaches produce estimates, with reliability depending on the quality of the information, assumptions and emission factors used.
Combining methods can be practical, particularly when some event activities have detailed records and others don't.
You don't necessarily need to choose one approach for your entire event, different emissions sources may be assessed using different methods, provided they're appropriate and don't result in double counting.
What Are Spend-Based Emissions?
Spend-based carbon accounting estimates greenhouse gas emissions using the amount of money spent on a product or service.
Rather than collecting detailed information about every item purchased, you use expenditure data and an appropriate monetary emission factor.
For example, imagine you've spent £2,000 on printed materials for a conference, but your supplier hasn't provided the weight or material composition of each item.
A spend-based calculation could use the expenditure and a suitable emission factor to estimate the emissions associated with that purchase.
Spend-based emissions = expenditure × relevant monetary emission factor
These factors are commonly derived from environmentally extended input-output models, often shortened to EEIO.
Put simply, these models connect economic activity with estimated greenhouse gas emissions across different industries and supply chains.
The GHG Protocol's Scope 3 Calculation Guidance recognises spend-based calculations as an approach for estimating emissions associated with purchased goods and services when more detailed methods aren't feasible.
When Is Spend-Based Carbon Accounting Useful for Events?
Spend-based calculations can be particularly helpful for event teams that already have access to budgets, invoices and purchasing records but don't have the resources to collect detailed information from every supplier.
This might include:
University events teams organising conferences, lectures and networking events alongside other responsibilities.
Small businesses arranging company meetings, launches or staff events.
Event agencies looking for an initial understanding of emissions associated with relevant purchases.
Organisations beginning carbon tracking that want to identify areas worth investigating in more detail.
Busy event organisers who need a preliminary estimate for internal planning.
For these teams, spend-based carbon accounting can provide a useful starting point without requiring every supplier to provide detailed physical information.
What Are the Limitations of Spend-Based Emissions?
Spend-based calculations typically rely on industry averages rather than the specific characteristics of individual purchases.
For example, two suppliers might provide similar products at different prices. A spend-based calculation could produce different emissions estimates because the expenditure differs, even when the physical emissions associated with those products are similar.
Price inflation can also affect spend-based results without necessarily reflecting changes in physical emissions.
This means spend-based estimates are particularly useful for initial assessments and relevant purchasing categories, but they may be less suitable for evaluating specific changes to materials or production methods.
What Are Activity-Based Emissions?
Activity-based carbon accounting estimates greenhouse gas emissions using information about what physically happened during an event.
Instead of starting with how much something cost, you use quantities, distances, consumption figures or other relevant activity data.
For example:
Kilowatt-hours (kWh) of electricity consumed by a venue.
Kilometres travelled by attendees using different transport methods.
Litres of fuel consumed by generators.
Kilograms of materials purchased for event production.
Quantities and types of meals served.
Kilograms of waste collected and how it was treated.
The activity data is multiplied by an appropriate emission factor to calculate estimated greenhouse gas emissions.
Activity-based emissions = activity data × relevant emission factor
The results are commonly expressed in kilograms or tonnes of carbon dioxide equivalent (CO₂e), a unit used to express the climate impact of different greenhouse gases on a comparable basis.
For UK activities, the government's 2026 greenhouse gas reporting conversion factors provide factors for activities such as electricity use, fuel consumption and transport.
If you're new to carbon calculations, our guide to emission factors explains how everyday operational information is converted into estimated emissions.
When Is Activity-Based Carbon Accounting Useful for Events?
Activity-based methods can be particularly valuable when you want to understand which activities contribute to your event's emissions and explore how different planning decisions might affect them.
For example, knowing the distances attendees travelled and their transport methods provides more specific information than knowing only how much was spent on travel.
Similarly, venue electricity consumption can provide a more relevant basis for calculating electricity-related emissions than the total venue hire cost.
Activity-based methods can be useful for:
Measuring attendee, staff and supplier travel.
Calculating venue electricity and fuel use.
Assessing event production materials and equipment.
Understanding catering-related emissions.
Reviewing waste quantities and treatment methods.
Comparing similar events using consistent calculation boundaries and methods.
This additional detail can help organisers understand which event activities are associated with emissions and which areas might benefit from further investigation.
What Are the Limitations of Activity-Based Emissions?
The main challenge with activity-based calculations is often collecting the necessary information.
You might need electricity consumption figures from your venue, material weights from your production supplier, travel information from attendees or catering quantities from your food provider.
For smaller teams managing several events, gathering all this information can take time.
Activity-based calculations also depend on the quality of the information collected and the suitability of the emission factors applied.
Although they can provide more detailed and representative estimates, they don't automatically produce exact results.
Spend-Based vs Activity-Based Emissions: Comparison Table
Spend-based method | Activity-based method | |
Information used | Financial expenditure | Physical activity or consumption data |
Event example | Cost of printed materials | Weight and material type of printed items |
Typical data sources | Invoices, budgets and purchasing records | Meter readings, travel records and supplier quantities |
Time and effort | Often quicker when financial records are available | Can require more detailed data collection |
Level of detail | Broad, category-level estimates | More specific information about individual activities |
Main advantage | Accessible starting point for initial assessments | Greater visibility into operational choices |
Main limitation | Influenced by prices and industry averages | Depends on the availability and quality of activity data |
Useful for | Initial estimates and relevant purchasing categories | Detailed assessments and evaluating operational changes |
Both approaches have a place in event carbon tracking. The most suitable method depends on what you're measuring, the information available and how you intend to use the results.
How Can Small Event Teams Calculate Emissions Quickly?
For smaller event teams, collecting carbon data is often one responsibility among many.
Imagine a university events department organising several conferences, departmental meetings and networking events throughout the year.
The team already manages budgets, suppliers, registrations, venues and event communications. It wants to understand the emissions associated with its events, but collecting detailed data from every supplier isn't always realistic.
In this situation, easy event carbon tracking starts with the information the team already holds, rather than waiting until every activity can be assessed in detail.
A practical approach is to work through the following steps.
1. Start With Your Existing Event Data
Begin by reviewing the records already available to your team.
These might include:
Event budgets and supplier invoices.
Catering and production expenditure.
Travel and accommodation bookings.
Venue electricity information.
Attendance figures.
Equipment hire and purchasing records.
Financial information may support spend-based calculations for relevant purchases, while other records may already contain useful activity data.
Starting with what you have can help you understand which emissions sources are relatively straightforward to assess and where information is missing.
2. Use Activity-Based Data Where It's Available
Not every event activity needs to be calculated using expenditure.
If you already know how much electricity your venue consumed, the distance staff travelled or the quantity of materials purchased, you may be able to use that information for more specific calculations.
For example, venue electricity consumption in kWh is generally a more appropriate basis for calculating electricity-related emissions than the overall cost of hiring the venue.
Using available activity data alongside suitable spend-based estimates can help you build an initial picture without creating unnecessary data collection work.
3. Record Your Estimates and Information Gaps
An initial event emissions assessment may include information collected directly from suppliers, estimates based on reasonable assumptions and calculations using financial expenditure.
It's important to record which approach you've used for each emissions source.
You might know how much was spent on signage but not the material weights, or have attendee numbers without complete travel information.
Where suitable estimation methods exist, these gaps don't necessarily prevent you from starting an assessment.
This is particularly relevant when you're trying to understand an event carbon footprint without complete data.
However, missing information should be clearly identified, and estimates shouldn't be presented as exact measurements.
Our guide to estimating carbon emissions explains how organisations can approach carbon calculations when complete information isn't available.
4. Improve Your Data Over Time
Once you've completed an initial assessment, you can review which information would be most useful to collect for future events.
You might decide to request electricity consumption figures from venues, collect attendee travel information during registration or ask production suppliers for material weights.
Over time, this can help your team move towards more detailed calculations where they provide additional value.
For practical advice, read our guide on how to improve your carbon data over time.
Can You Combine Spend-Based and Activity-Based Methods for One Event?
Combining spend-based and activity-based calculations can be a practical approach when different types of information are available across your event.
For example, you might have detailed attendee travel information and venue electricity data, but only financial records for certain production purchases.
Rather than using the same method for every category, you can select an appropriate approach for each emissions source.
Event activity | Information available | Possible calculation approach |
Attendee travel | Transport methods and journey distances | Activity-based |
Venue electricity | Electricity consumption in kWh | Activity-based |
Printed materials | Supplier invoice only | Spend-based |
Event production | Material quantities, weights and purchase or hire information | Appropriate activity-based or spend-based approach |
Catering | Meal numbers and food categories | Activity-based estimate |
Selected smaller purchases | Purchasing records | Spend-based, where suitable |
Using different methods across an event requires care to ensure that emissions aren't counted more than once.
For example, if you've already calculated emissions associated with a purchased item using its material weight, you shouldn't also add a separate spend-based estimate for the same item and emissions boundary.
It's also important to check that your emission factors cover the relevant activities and that any exclusions or assumptions are documented.
The GHG Protocol allows combinations of material-based and spend-based calculations for purchased goods and services. Its formally defined hybrid method, however, refers to a more specific approach involving supplier-specific and secondary data, so these terms shouldn't automatically be treated as interchangeable.
For event organisers working with multiple suppliers, our guide to tracking your Scope 3 supply chain for events explains why supplier information can be an important part of event carbon accounting.
How Scope Carbon Tracking Supports Different Calculation Approaches
At Scope Carbon Tracking, we recognise that different event teams have different resources, responsibilities and access to information.
A university events department organising several smaller conferences may not have the same data collection capacity as an agency managing a large international event.
Both teams may want to understand their event emissions, but the information available to them can be very different.
Scope's event carbon tracking software supports different approaches to calculating and estimating emissions, including spend-based calculations for relevant purchases, activity-based methods and other estimation options within supported modules.
This flexibility allows organisers to work with the information they have, while collecting more detailed data where it's useful.
Graphics and Print: Material Method or Spend Based
Scope's Graphics & Print module includes Material Method and Spend Based options.
When you have detailed information about the materials used, including dimensions, quantities and material weights, you can use the material-based approach.
When relevant purchasing information is available but physical material details aren't, the spend-based option provides an alternative way to estimate emissions.
For a team managing multiple events, this can be particularly helpful when suppliers provide different levels of information.
Event Catering: Actual Data or Estimates
Scope's Event Catering module provides Actual and Estimate options.
The estimate workflow shown in the platform allows organisers to enter information about meal types, food categories and the number of covers.
This highlights an important distinction between spend-based calculations and other estimation methods.
An estimate based on the number and type of meals served is not necessarily spend-based, because it uses information about the catering activity rather than the amount spent.
For organisers who don't yet have complete supplier information, this type of estimation can provide another way to begin assessing catering-related emissions.
You can explore this topic further in our guide to event catering emissions.
Waste Management: Actual Quantities or Estimates
Scope's Waste Management module includes options to record actual waste information or estimate quantities using event information such as attendance and duration.
This can be useful when an event organiser doesn't yet have final waste collection figures.
An attendance-based estimate is different from a spend-based calculation, but both demonstrate how alternative data can be used when detailed information is unavailable.
Travel and Accommodation: Activity-Based Information
Scope includes separate areas for staff, guest and supplier travel and accommodation.
These allow organisers to record information such as transport methods, journeys and distances, with separate areas for different traveller groups.
Keeping these activities organised can help event teams collect more specific information and reduce the risk of recording the same journey more than once.
If you're looking to improve travel data collection, our guide to tracking attendee travel emissions offers a practical starting point.
Production, Energy and Other Event Activities
Scope also provides modules covering production and build, energy and water, supplier logistics, and online or hybrid attendees.
Each module collects information relevant to the activity being assessed. For example, production records can include item quantities, hire or purchase costs and reuse status, while energy calculations use relevant consumption information.
The available calculation and estimation methods vary by module, so not every area uses spend-based calculations or offers identical Actual and Estimate options.
The aim is to help event teams build an emissions assessment using appropriate information for different activities, rather than relying on one calculation method for everything.
You can find out more about these capabilities on our Event Carbon Tracking page.
How to Prepare a Quick Event Emissions Report
If you're looking for a quick event emissions report for an internal update, planning meeting or initial sustainability assessment, it helps to establish what the report needs to communicate before collecting additional information.
A preliminary assessment may not require the same level of detail as a formal emissions disclosure or independently assured inventory.
However, it should still explain what has been included, which calculation methods have been used and where estimates or assumptions affect the results.
A practical checklist is:
Define the event: record the dates, location, attendance and activities being assessed.
Set the assessment boundary: identify which emissions sources are included and note any exclusions.
Gather available information: review invoices, purchasing records, travel information and relevant supplier data.
Select appropriate calculation methods: use activity-based data where available and suitable spend-based estimates for relevant purchasing categories.
Document assumptions: record estimated values, missing information and emission factors.
Review the results: identify which emissions categories appear significant and where more detailed information may be useful.
Explain the limitations: make clear whether the results are preliminary estimates or part of a more detailed assessment.
This approach can support simple event carbon reporting for internal planning, while making clear that the results may be preliminary.
A quick event carbon footprint calculation can provide a useful starting point, but the result shouldn't automatically be described as a complete or independently verified event emissions report.
If your organisation needs to meet a particular reporting standard, contractual requirement or disclosure obligation, check the applicable methodology and evidence requirements.
For a broader explanation of the activities that can contribute to an event footprint, see our guide to measuring and reducing your event carbon footprint.
Is Activity-Based Carbon Accounting Always Better?
Activity-based calculations can provide more detailed information about the activities associated with emissions, which is particularly useful when reviewing transport arrangements, energy consumption or event production choices.
However, that doesn't mean activity-based calculations are always the most practical starting point for every event team.
If detailed information isn't available, a suitable spend-based calculation can help you begin estimating emissions associated with certain purchases.
Spend-based calculations can provide a broad estimate based on expenditure, while activity-based calculations can offer greater insight into the physical activities behind the result.
As more information becomes available, your team can improve its calculations and develop a clearer understanding of emissions across future events.
For many organisers, the most useful approach is one that balances available resources, data quality and the purpose of the assessment.
Frequently Asked Questions About Spend-Based and Activity-Based Emissions
What Is the Difference Between Spend-Based and Activity-Based Emissions?
Spend-based emissions calculations use financial expenditure and monetary emission factors, while activity-based calculations use physical information such as electricity consumption, travel distances or material quantities.
Both approaches estimate greenhouse gas emissions, but they use different types of data and can provide different levels of detail.
Is Spend-Based Carbon Accounting Accurate Enough for Events?
Spend-based carbon accounting can provide useful initial estimates for relevant event purchases when more detailed information isn't available.
However, the results rely on monetary emission factors and industry averages, which may not reflect the specific characteristics of your purchases. Whether the method is suitable depends on the purpose of the assessment and any reporting requirements.
What Is the Quickest Way to Estimate an Event's Carbon Footprint?
The quickest practical way to begin estimating an event's carbon footprint is often to start with information you already have, including invoices, purchasing records, attendance figures and available activity data.
Spend-based calculations can support estimates for suitable purchasing categories, while existing activity information can be used for more specific calculations.
The time required will depend on the event, available records and the level of detail needed.
Can I Calculate Event Emissions Using Only Invoices?
Event emissions can be estimated from invoices for certain purchasing categories using suitable spend-based emission factors.
However, invoices alone may not provide enough information to assess every event activity appropriately. Electricity consumption, travel distances and fuel use, for example, are generally better assessed using relevant physical activity data.
Can I Use Spend-Based and Activity-Based Methods Together?
Spend-based and activity-based methods can be used together for different event activities, provided the calculations use suitable emission factors, follow appropriate boundaries and avoid double counting.
For example, an organiser might use activity-based information for attendee travel and spend-based estimates for selected production purchases.
Does Scope Carbon Tracking Offer Both Methods?
Scope Carbon Tracking supports spend-based calculations for relevant event purchases and activity-based approaches across different event modules.
Its Graphics & Print module includes Material Method and Spend Based options, while other modules offer different ways to record activity information or calculate estimates.
The methods available depend on the event activity being assessed.
How Can Small University Events Teams Start Tracking Carbon Emissions?
University events teams can begin by reviewing existing budgets, invoices, venue information, attendance figures and supplier records.
Suitable spend-based estimates can provide a starting point for relevant purchases, while activity data can be used where it's available.
As the team develops its process, it can identify information gaps and collect more detailed data for future events.
How Can I Improve the Accuracy of My Event Emissions Estimates?
Improving event emissions estimates involves reviewing the quality of your existing data, identifying important information gaps and collecting more specific activity information where appropriate.
For example, you might request electricity consumption figures from venues, ask suppliers for material details or collect attendee travel information during registration.
Consistent calculation boundaries, suitable emission factors and clear documentation are also important when comparing results over time.
Start Tracking Your Event Emissions With the Data You Have
Whether you're organising a university conference, a company meeting or a larger programme of events, the most suitable carbon tracking approach will depend on your team's resources and the information available.
Spend-based and activity-based calculations offer different ways to understand emissions associated with your events.
Spend-based methods can help you get started with relevant purchasing information, while activity-based methods can provide more detailed insight into the activities contributing to your footprint.
Using both approaches where appropriate can help you build an initial assessment and improve the information behind your calculations over time.
With Scope Event Carbon Tracking, organisers can record information across different event activities, use supported calculation and estimation methods, and review the emissions associated with their event data.
Explore our Event Carbon Calculator or find out more about how Scope can support your event carbon tracking process.
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