Every carbon or nature footprint ekko returns is an estimate, calculated from the organisation's country, its sector and the purchase amount. Equivalents turn that estimate into a comparison a consumer recognises, like a short flight or a football pitch. This page explains what each comparison is based on, so you have a credible source behind every number your organisations and consumers see.

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Estimates, not exact measurements
A carbon or nature footprint is a modelled estimate. An equivalent restates that estimate as a familiar comparison. Neither is a precise measurement of a single transaction, and the wording is chosen to reflect that.

What an equivalent is

An equivalent translates an abstract figure into something tangible. Carbon footprints are measured in grams of CO² equivalent (gCO²e). Nature footprints are measured in mean species abundance per square metre (MSA m²). Both are hard to picture on their own.

Rather than only showing a raw figure, ekko also returns comparisons:

"That's like 2 flights from London to Edinburgh" for a carbon figure
"That's as much as a tree can capture in 3 months" for a carbon figure
"That's the size of 4 parking spaces" for a nature figure

Each comparison is scoped either to a country, using a route or reference familiar in that market, or applied globally, like a tree or a football pitch.

Where each figure comes from

Every equivalent is calculated from a named, published source.

Comparison	Source
Flights	DEFRA 2024 GHG Conversion Factors for Company Reporting (UK Government)
Trains	The rail operator's own sustainability disclosure where one exists, otherwise a national rail average, scoped per country
Trees, wind and seagrass	IEA, the European Environment Agency and peer-reviewed research, for example Fourqurean et al. 2012 in Nature Geoscience
Household comparisons	Recognised carbon benchmarks, for example Mike Berners-Lee, "How Bad Are Bananas?"
Area references	The sport's world governing body or a national standard, for example FIFA, World Rugby, ITF, the NFL and the UK Department for Transport

Two examples of how a figure is built:

Flights use the DEFRA 2024 economy-class factor with a radiative forcing multiplier, multiplied by the great-circle distance between the two airports.
Trains use the operator's published figure where available, such as SNCF, NS or Deutsche Bahn, so a French rail comparison reflects France's low-carbon grid rather than a global average.