Sponsors, corporate clients, and attendees are increasingly asking the same question after an event: what was its carbon footprint? A credible event sustainability report answers that with numbers, not adjectives. This guide walks through how to measure your event's emissions, where those emissions actually come from, and how to turn the data into a report people can trust.
What an event carbon footprint includes
An event carbon footprint is the total greenhouse gas emissions caused by your event, expressed in tonnes of carbon dioxide equivalent (tCO2e). Most reports organize emissions using the three scopes of the GHG Protocol:
- Scope 1: Direct emissions from sources you control, such as fuel burned in generators or vehicles you operate.
- Scope 2: Emissions from electricity, heating, or cooling you purchase.
- Scope 3: Everything else in your value chain: attendee and staff travel, hotel stays, the venue's energy, food and beverage, materials, shipping, and waste.
For most event organizers, nearly all event emissions fall in Scope 3. You don't own the venue, the planes, or the hotels, but your event is the reason those emissions happen.
Where event emissions actually come from
Travel dominates. In the Global Business Travel Association's published footprint for its 4,600-attendee convention, attendee travel accounted for about 81% of total emissions, and the event came to roughly 1.02 tCO2e per attendee (GBTA event footprint report).
| Category | Share of total emissions |
|---|---|
| Attendee travel (including hotel stays) | About 81% |
| Shipping | About 8% |
| Event venue energy | About 4% |
| Staff travel | About 1% |
| Food and beverage | About 1% |
| Materials | Under 1% |
Shares calculated from the category totals in the GBTA report. Your mix will differ by destination, audience, and format, but the pattern holds for most in-person conferences: where attendees travel from shapes your footprint far more than anything on-site.
Pro tip: Report per-attendee emissions alongside the total. A growing event will almost always have a larger total footprint, but a falling per-attendee figure shows real progress.
How to measure your event's emissions
The basic formula is simple: activity data × emission factor = emissions. Activity data is what you measure (miles flown, kilowatt-hours used, meals served). Emission factors convert that activity into CO2e. Free factor sets include the US EPA GHG Emission Factors Hub and the UK government's annual greenhouse gas conversion factors.
1. Set your boundary
Decide what's in and out before the event: attendee travel, staff travel, hotels, venue energy, F&B, materials, shipping, and waste. Write it down. A clear boundary makes your report comparable from year to year.
2. Collect travel data at registration
Add two questions to your registration form: departure city or postal code, and planned travel mode. That one change turns your biggest emissions category from a guess into a calculation. Our guide to event registration forms covers how to add questions without hurting completion rates.
3. Ask the venue and hotels for their numbers
Request actual electricity, gas, and water use for your event days from the venue, and room nights from your hotel block. Put this in the contract up front; it's much easier to get when it's agreed before the event.
4. Track food, materials, and shipping
Use your final catering counts by meal type, the weights of printed materials, signage, and booth builds, and the weights and distances of everything shipped in. Ask suppliers for their sustainability data; many already have it.
5. Calculate and document your method
Apply emission factors to each category, and record which factors and assumptions you used. If you sample attendee travel and extrapolate, say so. Transparency about method is what makes a report credible.
What to include in an event sustainability report
- Boundary and method: What you measured, what you excluded, and which emission factors you used.
- Total emissions: In tCO2e, broken down by category and scope.
- Intensity: Emissions per attendee, and per event day for multi-day events.
- Reductions: What you changed this year and its measured effect.
- Offsets, reported separately: If you purchase offsets, list them apart from your actual emissions, with the project type and standard.
- Next-year targets: Specific, measurable goals tied to your biggest categories.
Heads up: Avoid calling an event "carbon neutral" based on offsets alone. Industry guidance from the Net Zero Carbon Events initiative stresses that offsetting isn't the path to net zero; reducing emissions comes first.
Frameworks and standards worth knowing
- Net Zero Carbon Events: An industry pledge launched at COP26 in November 2021 and facilitated by the Joint Meetings Industry Council. Signatories commit to halving emissions by 2030 and reaching net zero by 2050, publishing a pathway, and reporting progress at least every two years. Its measurement methodology covers event emissions across nine categories.
- ISO 20121: The international standard for event sustainability management systems, updated in 2024. It sets out how to manage sustainability across your event process; it isn't a carbon calculator or a reporting format.
- GHG Protocol: The standard accounting framework behind Scope 1, 2, and 3 reporting, and the language your corporate clients' sustainability teams will expect.
If you want to build your own expertise, see our guide to earning a sustainable event professional certificate.
Where badges and lanyards fit
Materials are a small slice of most event footprints, but they're one of the easiest categories to document and improve, and attendees see them up close. When you choose badges and lanyards, look for suppliers that can give you clear material facts for your report.
- FSC-certified stock: Billy's Badges paper and direct thermal badges are FSC-certified.
- Cleaner production: Digital printing uses no printing plates or chemical developing, with biodegradable ink.
- Print on demand: Badges are printed to order, so no unused inventory is produced.
- Lower-impact lanyards and packaging: rPET lanyards made from recycled plastic, and compostable packaging.
Paper and unlaminated direct thermal badges skip the plastic altogether. For end-of-event disposal, check your local recycling program, since accepted materials vary by area. Learn more on our sustainability page or in sustainable event badge printing.
Measure the categories that matter most, document your method, and your sustainability report becomes a tool for improving next year's event, not just a summary of this one.
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Frequently asked questions
How do you calculate an event's carbon footprint?
Multiply activity data (miles traveled, kilowatt-hours of venue energy, meals served, kilograms of materials) by matching emission factors, such as those from the US EPA, then add the results across categories. Report the total in tCO2e, plus a per-attendee figure.
What is the biggest source of emissions at an event?
Attendee travel. In GBTA's published convention footprint, attendee travel including hotel stays made up about 81% of total emissions. Venue energy, food, and materials are much smaller shares.
What is the average carbon footprint per conference attendee?
It varies widely with how far attendees travel. GBTA's convention of more than 4,600 attendees came to roughly 1.02 tonnes of CO2e per attendee. Local or regional events can be far lower.
What should an event sustainability report include?
Your measurement boundary and method, total emissions by category and scope, emissions per attendee, the reductions you made, any offsets listed separately from actual emissions, and targets for next year.
Are event emissions Scope 1, 2, or 3?
For most organizers, nearly all event emissions are Scope 3, because they come from sources you don't own, such as attendee flights, hotels, and the venue's energy. Scope 1 and 2 apply only to fuel and energy you directly control or purchase.
What is ISO 20121?
ISO 20121 is the international standard for event sustainability management systems, most recently updated in 2024. It guides how you manage sustainability across your event planning process, rather than prescribing how to calculate or report emissions.