ISO 20121 Standard: Event Sustainability KPIs, Measurement and Reporting

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Introduction

Event sustainability is not measured by the number of green initiatives an organizer announces. It is measured by understanding what happens before, during, and after an event—and using that information to make better decisions.

An exhibition may introduce reusable materials. A conference may encourage attendees to use public transport. A festival may change its catering arrangements to reduce food waste. These are useful initiatives, but organizers still need to understand whether the changes deliver the intended results.

The ISO 20121 standard provides a management-system framework for addressing sustainability in event-related activities. Within this framework, key performance indicators (KPIs), data collection, and reporting can help organizations evaluate their progress and identify opportunities for improvement.

This guide focuses specifically on measuring event sustainability performance. It explains how to select appropriate indicators, establish baselines, calculate useful metrics, collect reliable data, and prepare meaningful post-event reports.

The aim is to help event organizers turn sustainability objectives into practical measurements that support operational decisions and continual improvement.

For information about the broader requirements and certification process, visit the existing ISO 20121 certification page for the UAE.

What Is the ISO 20121 Standard?

ISO 20121 is an international standard for Event Sustainability Management Systems. The current published edition is ISO 20121:2024, titled Event sustainability management systems — Requirements with guidance for use. It replaced the 2012 edition.

The standard provides a framework for organizations that want to manage the environmental, social, and economic impacts associated with events and event-related activities.

For sustainability measurement, the important principle is that organizations should evaluate performance in a way that supports their objectives and management-system processes.

An event organizer might establish an objective to reduce waste per attendee. Another organization might prioritize transport-related emissions, accessibility, responsible procurement, or the performance of event suppliers.

The indicators should reflect the organization's activities, relevant sustainability issues, and intended outcomes. There is no single set of KPIs that is automatically suitable for every event.

KPI measurement is one part of a broader management system. Collecting sustainability figures alone does not establish conformity with ISO 20121.

What Are Event Sustainability KPIs?

Event sustainability key performance indicators are measures used to assess selected sustainability-related activities or outcomes.

They help organizers answer questions such as:

• How much waste was generated?
• What was the energy consumption during the event?
• How did attendees travel to the venue?
• What proportion of relevant suppliers met specified requirements?
• Were planned accessibility arrangements implemented?
• Did the event achieve its sustainability objectives?
• Which areas need improvement before the next event?

A KPI can be a total quantity, percentage, rate, ratio, or other clearly defined measure.

For example, an organizer could record the total waste generated at a conference. It could also calculate waste per attendee. The first figure shows the total quantity, while the second helps compare events of different sizes when their measurement methods are sufficiently consistent.

A useful KPI has a clear purpose, a defined calculation method, an identified data source, and an assigned owner. Without these elements, reported figures may be difficult to interpret or compare.

Why KPI Measurement Matters Under ISO 20121

Sustainability commitments are more useful when organizations can evaluate whether they are being achieved.

KPI measurement can help event teams:

Evaluate objectives: Compare actual performance with the targets established during planning.

Identify operational weaknesses: Recognize where waste, resource consumption, supplier performance, or other results differ from expectations.

Improve decision-making: Use evidence when selecting venues, materials, catering arrangements, transport options, and contractors.

Strengthen accountability: Assign responsibility for data collection and follow-up actions.

Support reporting: Communicate results using defined methods and explain the limitations of available data.

Encourage continual improvement: Use findings from one event to improve planning and delivery for future events.

The value of a KPI depends on how the organization uses it. A dashboard filled with figures may look impressive, but the measures should help management understand performance and determine what to do next.

Main Categories of Event Sustainability KPIs

The appropriate indicators depend on the event's size, format, location, supply chain, and sustainability priorities.

1. Waste Management KPIs

Events can generate food waste, packaging, disposable service items, printed materials, temporary construction materials, and general waste.

Waste-related indicators can help organizers understand how much waste is generated and whether prevention, reuse, recycling, and disposal arrangements are working as intended.

Possible KPIs include:

• Total waste generated.
• Waste generated per attendee.
• Waste generated per event day.
• Waste diversion rate, using a defined calculation method.
• Food waste per meal served.
• Quantity of selected materials reused.
• Percentage of relevant waste records received from contractors.

For example, an exhibition organizer may find that packaging and temporary stand materials account for a significant portion of its waste. This information could support revised exhibitor guidance, reusable stand designs, or changes to supplier arrangements.

Organizers should define what is included in the waste measurement. They should also distinguish between material collected for recycling and material confirmed as recycled, where the available evidence allows that distinction.

2. Energy Consumption KPIs

Energy may be used for venue lighting, heating and cooling, audiovisual equipment, catering, temporary installations, and generators.

Possible indicators include:

• Total electricity consumption within the reporting boundary.
• Generator fuel consumption.
• Energy consumption per attendee.
• Energy consumption per event day.
• Percentage of energy supplied from a specified source, where reliable information is available.

The data may come from venue meters, utility records, contractors, or other suitable sources.

Comparisons require care. A three-day exhibition using a large venue cannot automatically be compared with a one-day meeting in a smaller building. Event duration, venue area, attendance, and the services included may affect the result.

If event-specific energy data are unavailable, the organizer should explain the measurement limitations rather than present an unsupported estimate as an exact figure.

3. Water Consumption KPIs

Water consumption may be particularly relevant to outdoor festivals, multi-day events, catering operations, temporary facilities, and events held in locations where water availability is a significant concern.

Possible measures include:

• Total water consumption within the defined event boundary.
• Water consumption per attendee.
• Water consumption per event day.
• Completion of planned water-efficiency actions.
• Recorded water-related operational issues.

Water use per attendee can be useful when comparing similar events, but it should be interpreted in context. Catering, accommodation, weather, venue facilities, and event duration may influence consumption.

The organization should also distinguish between directly measured consumption and estimated usage.

4. Transportation and Travel KPIs

Attendee travel and event logistics can be important sustainability considerations, especially for large exhibitions, sporting events, festivals, and international conferences.

Possible indicators include:

• Percentage of surveyed attendees using specified transport modes.
• Number of passengers using event shuttle services.
• Distance travelled by selected event logistics vehicles.
• Estimated transport-related greenhouse gas emissions.
• Percentage of attendees providing usable travel-survey responses.

An attendee survey can help identify travel patterns and opportunities to improve transport planning.

However, survey results depend on the number and characteristics of respondents. Organizers should document the survey method, response rate, assumptions, and limitations.

If emissions are estimated, the calculation should identify the activity data, emission factors, boundaries, and assumptions used. Results from different events should not be treated as directly comparable if their calculation methods differ significantly.

5. Procurement and Supplier KPIs

Event suppliers can influence sustainability performance through the materials, equipment, food, transport, staffing, and services they provide.

Procurement indicators can help organizations assess how consistently relevant sustainability requirements are incorporated into purchasing and contractor arrangements.

Examples include:

• Percentage of relevant suppliers assessed against defined criteria.
• Percentage of applicable contracts containing specified sustainability requirements.
• Percentage of priority suppliers providing requested performance data.
• Number of supplier-related issues resolved.
• Percentage of selected equipment or materials reused across events.

Each indicator needs a clear definition.

For instance, the supplier assessment rate should specify which suppliers are included in the calculation and what qualifies as a completed assessment. Sending a questionnaire does not necessarily demonstrate that a meaningful assessment has taken place.

Organizations should consider both the completion of procurement activities and the actual performance of relevant suppliers.

6. Social Sustainability KPIs

Event sustainability also involves people, working conditions, accessibility, inclusion, and relationships with affected communities.

Depending on the event, indicators may include:

• Completion of planned accessibility checks.
• Number of accessibility issues reported and resolved.
• Percentage of relevant personnel completing required training.
• Stakeholder feedback scores using a defined method.
• Worker welfare concerns recorded and addressed.
• Completion of planned stakeholder engagement activities.

For example, an event organizer may review whether attendees received suitable accessibility information before the event and whether identified access barriers were addressed.

Overall satisfaction scores should not conceal individual concerns. Feedback should be reviewed alongside complaints, specific comments, and corrective actions where relevant.

7. Economic and Resource-Efficiency KPIs

Economic measures can help organizations understand how sustainability decisions affect resource use, procurement, and event costs.

Possible indicators include:

• Waste management costs within the reporting boundary.
• Cost per attendee for selected services.
• Documented savings from reusing equipment.
• Percentage of selected equipment reused across events.
• Expenditure with local suppliers, where relevant and consistently defined.

These indicators should be interpreted alongside environmental and social considerations.

For example, a supplier with a lower initial price may not offer the best overall outcome if its services require more transport, create additional waste, or fail to meet specified requirements.

The purpose is to support balanced decisions rather than to prioritize cost savings at the expense of other relevant sustainability objectives.

How to Select the Right KPIs for an Event

An organization does not need to measure everything. It needs to select indicators that help it understand its most relevant sustainability issues and evaluate progress against its objectives.

Step 1: Identify significant sustainability issues

Review the event's activities, services, stakeholders, and operating conditions.

A large outdoor festival may prioritize waste, water, transport, temporary infrastructure, and community impacts. A corporate conference may focus on travel, venue energy, catering, accessibility, and suppliers.

The selection should reflect the event's actual circumstances.

Step 2: Connect indicators to objectives

Every major KPI should have a clear reason for being measured.

If the objective is to reduce waste per attendee, the organization needs reliable waste and attendance data. If the objective is to improve supplier performance, it must define the supplier population, assessment criteria, and expected outcome.

This connection prevents the organization from collecting data that does not support a decision.

Step 3: Define the measurement method

For every KPI, document:

• The indicator name and purpose.
• The unit of measurement.
• The reporting boundary and period.
• The data source.
• The calculation method.
• Relevant assumptions.
• The person responsible for collecting and reviewing the data.

These details make results easier to understand and compare.

Step 4: Assign responsibility

Data collection often involves multiple parties.

The event manager may coordinate the reporting process, while the venue supplies energy data, the waste contractor provides waste records, procurement monitors supplier assessments, and the attendee services team collects feedback.

Clearly assigned responsibilities reduce the likelihood of missing or inconsistent information.

Step 5: Check whether the data are available

Before setting a target, determine whether the organization can obtain the information needed to evaluate it.

If a venue cannot provide event-specific water data, the organizer may need to agree on an alternative measurement approach.

Where estimates are used, document the method and explain the limitations.

Step 6: Establish a baseline and target

A baseline provides the reference point against which future performance is evaluated.

Targets may be based on previous comparable events, operational information, contractual commitments, or other defensible evidence.

Avoid choosing a reduction percentage simply because it sounds ambitious. Targets should be appropriate to the organization's circumstances and supported by a method for evaluating progress.

Step 7: Review results and take action

Compare actual performance with the baseline and target.

Identify important differences, consider what the available evidence shows, and decide whether corrective action or a change in planning is needed.

The results should inform future event arrangements rather than remain in a report that no one uses.

How to Calculate Event Sustainability KPIs

The following formulas are illustrative methods for measurement. They are not universal formulas prescribed by ISO 20121.

Waste per attendee

Formula:

Waste per attendee = Total waste generated ÷ Number of attendees

Example:

An event generates 600 kg of waste and records 1,200 attendees.

600 kg ÷ 1,200 attendees = 0.5 kg per attendee.

The organization should define which waste streams and event activities are included and use a consistent attendance measure.

Waste diversion rate

Formula:

Waste diversion rate (%) = Quantity of waste diverted under the defined method ÷ Total waste generated × 100

Example:

An event records 800 kg of total waste. Of this, 320 kg is verified as diverted under the organization's reporting method.

320 ÷ 800 × 100 = 40%.

The organization should define the qualifying diversion routes and support the result with appropriate records.

Supplier assessment rate

Formula:

Supplier assessment rate (%) = Number of relevant suppliers assessed ÷ Total relevant suppliers in scope × 100

Example:

An organizer assesses 36 of 45 relevant suppliers.

36 ÷ 45 × 100 = 80%.

This indicates the proportion of suppliers assessed. It does not automatically prove that those suppliers meet every sustainability requirement.

Training completion rate

Formula:

Training completion rate (%) = Number of relevant personnel who completed the specified training ÷ Total personnel required to complete it × 100

Example:

If 90 of 100 relevant personnel complete the specified training, the completion rate is 90%.

The organization should also consider whether the training was suitable and whether personnel can apply the relevant procedures.

Objective achievement rate

An organization with multiple measurable objectives may calculate the proportion achieved.

Formula:

Objective achievement rate (%) = Number of defined objectives achieved ÷ Total objectives included in the evaluation × 100

This figure should be interpreted carefully. Unless a weighting method is used, it treats each objective equally and does not show the relative importance of the objectives.

A serious unmet objective should not be hidden by a high overall percentage.

Establishing a Reliable Sustainability Baseline

A baseline is a reference point used to evaluate change over time.

For event sustainability, it may be based on a previous edition of the same event, a comparable event, an initial measurement period, or another documented reference appropriate to the objective.

A useful baseline should identify the event or activity being measured, the reporting period, the units, the measurement boundary, the data source, and relevant assumptions.

Suppose an annual exhibition wants to reduce waste per attendee. Comparing its latest results with the previous year may be useful, but the organization should consider whether the venue, attendance, event duration, catering arrangements, and waste contractor remained comparable.

Total waste may increase when an event grows, even if waste per attendee decreases. Reporting both figures provides a more balanced view.

If the measurement method changes, the organization should document the change and explain whether historical results remain comparable.

Collecting Data Before, During and After an Event

Data collection is more reliable when it is planned as part of normal event operations.

Before the event

Define the indicators, data sources, reporting boundaries, responsibilities, and targets.

Coordinate with venues and suppliers early. If energy use is an important KPI, establish whether the venue can provide event-specific consumption data and how the reporting period will be defined.

If attendee travel is being measured, prepare the survey and decide how responses will be collected and evaluated.

During the event

Record information according to the agreed methods.

This may include waste records, resource consumption, supplier performance, training completion, accessibility issues, and attendee feedback.

Assign responsibility for checking missing information and documenting relevant operational changes.

After the event

Collect outstanding supplier data, verify calculations, compare results with targets, and document relevant limitations.

The post-event review should identify what worked, what fell short, and which changes should be considered for future events.

Where corrective actions are necessary, assign responsibilities and appropriate follow-up dates.

Common Mistakes in Event Sustainability Reporting

Reporting figures without defining the boundary

An organizer may report venue electricity consumption but exclude temporary generators or setup days. If the exclusions are not explained, the figure may create a misleading impression.

Define the measurement boundary before collecting data.

Changing calculation methods between events

Different attendance-counting methods, waste measurements, or emission factors can affect the reported result.

Document methodology changes and avoid presenting results as directly comparable when the underlying methods differ significantly.

Reporting only successful results

A report that describes successful initiatives but omits missed targets provides an incomplete picture.

Include relevant gaps, explain what the evidence shows, and identify corrective actions.

Treating estimates as exact measurements

Travel emissions, estimated waste quantities, and supplier data may involve assumptions or uncertainty.

Identify estimates clearly and document the calculation method and relevant limitations.

Measuring activity instead of outcomes

Holding a sustainability training session is an activity. Training completion measures participation. Whether the training improved awareness or operational performance is a separate question.

Choose indicators that distinguish actions taken from results achieved.

Collecting too many indicators

A large KPI dashboard may create unnecessary administration without improving decisions.

Prioritize indicators linked to significant impacts and practical objectives. Add more only when the additional information has a clear purpose.

What Should an Event Sustainability Report Include?

A post-event sustainability report should provide a clear picture of performance and identify opportunities for improvement.

A practical report may include:

Event overview: Describe the event, its duration, relevant activities, and reporting boundary.

Sustainability objectives: List the objectives and explain their relevance to the event.

KPI definitions: State the indicators, units, calculation methods, and data sources.

Baselines and targets: Identify the reference points and intended results.

Actual performance: Present results and compare them with targets or previous comparable events.

Data limitations: Explain missing information, estimates, assumptions, and methodology changes.

Interpretation: Discuss relevant factors that may have influenced the results without claiming causes that the evidence cannot establish.

Stakeholder feedback: Summarize relevant feedback while protecting personal information.

Corrective actions: Identify gaps, responsibilities, deadlines, and methods for checking completion.

Future improvements: Record changes to consider when planning the next event.

The amount of reporting should be proportionate to the event and the organization's needs. A small internal conference may require a concise record, while a large public event may need more detailed evidence and analysis.

Practical Example: Measuring Sustainability at an Exhibition

Consider an exhibition organizer that wants to improve waste management and supplier performance.

Before the exhibition, the organization reviews previous waste records and defines the reporting boundary. It agrees with the venue and waste contractor on how quantities will be recorded. Procurement identifies the suppliers that need to be assessed against specified sustainability criteria.

During the event, waste quantities are recorded using the agreed method. The procurement team tracks completed assessments and records relevant supplier issues.

After the exhibition, the organizer compares the results with its baseline and objectives.

The analysis shows that supplier assessment coverage improved, but total waste increased. Rather than immediately concluding that waste controls failed, the team checks attendance, the number of exhibitors, packaging practices, and the available contractor records.

Based on the evidence, the organization may revise exhibitor instructions, improve collection arrangements, or agree on packaging requirements with selected suppliers.

This example illustrates the purpose of KPI measurement: understand the results, assess the available evidence, and use the findings to improve future event planning.

Using KPI Results for Continual Improvement

Collecting data is only one part of effective sustainability management. Organizations need to use the results to guide decisions.

When a target is missed, the organization should evaluate the circumstances and determine whether corrective action is appropriate.

For example, a low waste diversion rate might be associated with unclear signage, unsuitable collection facilities, contamination, contractor coordination, or incomplete data. The correct response depends on the available evidence.

A successful result also deserves review. The organization should determine whether the same approach is likely to work for future events with different venues, suppliers, audiences, and operational requirements.

A practical improvement cycle is:

1. Define the sustainability objective.
2. Select an appropriate KPI.
3. Establish a baseline and target.
4. Collect and check the data.
5. Evaluate the result.
6. Identify gaps and relevant causes.
7. Assign and implement improvement actions.
8. Review the effectiveness of those actions at the next appropriate opportunity.

This approach can support the performance evaluation and continual improvement processes of an Event Sustainability Management System.

How KPI Measurement Relates to ISO 20121 Certification

KPI measurement can support an organization's ISO 20121 management-system processes, but a collection of sustainability metrics does not, by itself, establish conformity with the standard.

Organizations need to address the applicable requirements, determine relevant sustainability issues, establish appropriate objectives, implement operational controls, evaluate performance, and pursue improvement.

Certification is a separate conformity-assessment process. Organizations considering certification should confirm the intended scope of their management system and the applicable assessment arrangements.

For information about the broader requirements and certification process, see the existing SCS ISO 20121 certification page for the UAE.

For the official standard description and edition information, refer to the ISO 20121:2024 page.

Conclusion

The ISO 20121 standard provides a framework for managing sustainability in event-related activities. KPIs can help organizations evaluate selected aspects of performance, understand whether objectives are being achieved, and identify opportunities for improvement.

The most useful indicators are linked to relevant sustainability issues, supported by clear definitions, and based on reliable data. Consistent baselines, transparent assumptions, supplier coordination, and meaningful post-event reviews make the results more useful.

Event organizers do not need dozens of indicators to make progress. They need to measure the right things, understand the limitations of the information, and use the findings to improve decisions.

To discuss ISO 20121 certification-related requirements, contact SCS Certification.

https://scscertification.com/contactus.php

Disclaimer

This article is provided for general educational purposes. The KPI formulas and examples are illustrative measurement methods, not universal formulas prescribed by ISO 20121. Organizations should select suitable indicators and reporting methods for their activities and consult the applicable standard when developing an Event Sustainability Management System.