Where do I source the emission factors for a freight calculator?
From the GLEC Framework for anything crossing a border or a mode, and from DEFRA's delivery-vehicle and freight rows for UK fleets. GLEC is the logistics industry's method, aligned with ISO 14083; DEFRA publishes UK vehicle factors under an open licence.
A freight calculator is only as defensible as the factor behind the tonne-kilometre, and the two publishers that matter answer different questions. GLEC tells you what a container on a deep-sea vessel or a pallet on a European road network emits, per tonne-km, in a way a customer’s carbon report will accept. DEFRA tells you what a UK van or articulated lorry emits, per km or per tonne-km, from the government’s own annual set. Most calculators need both, and the boundary rules that stop them being double-counted.
Which publisher for which lane
| You are modelling | Source | Basis | Licence |
|---|---|---|---|
| Sea, air, rail or road freight across modes or borders | GLEC Framework v3.2 default factors | kg CO2e per tonne-km, well-to-wheel, by mode and vehicle or vessel class | Free with attribution; factor tables reproducible |
| UK vans, HGVs and delivery fleets | DEFRA GHG conversion factors, delivery vehicles and freight rows | kg CO2e per km or per tonne-km, by vehicle class and load | Open Government Licence v3.0 |
| A specific carrier or lane | The carrier’s own ISO 14083 declaration | Primary data; beats any default | The carrier’s terms |
| The boundary and allocation rules | ISO 14083; GHG Protocol Scope 3 categories 4 and 9 | Method, not values | Standards text, cited |
Explainers: the GLEC Framework, DEFRA conversion factors, the Scope 3 Standard.
What the corpus holds, by key
Four headline keys carry the GLEC defaults by mode: freight.road_hgv.tonne_km, freight.rail.tonne_km, freight.sea.tonne_km and freight.air.tonne_km. Beneath them, freight_detailed.* keys carry GLEC’s finer classes by region, mode and fuel, and DEFRA’s delivery-vehicle section holds 225 rows for UK vehicle classes. A search for “freight” across the corpus returns just under four hundred rows, each with its publisher and source reference. The freight factors page lists them; the travel and freight dataset offers the DEFRA rows as a file.
The boundary rules that decide the number
- Well-to-wheel, not tank-to-wheel. GLEC and ISO 14083 include fuel production. DEFRA publishes the two separately, as a direct factor and a well-to-tank factor; use both or you understate by a fifth or more.
- Load factor and empty running. A tonne-km default already assumes an average load and a share of empty return legs. Do not apply a second utilisation adjustment unless you replace the default with a carrier’s primary data.
- Categories 4 and 9 are different legs. Upstream transport you pay for is category 4; downstream distribution to your customer is category 9. Same factor, different line in the inventory.
- Vintage. Record the GLEC version and the DEFRA year on every calculation. Both move, and a calculator that mixes GLEC v3.0 rows with v3.2 rows is quietly inconsistent.
Build it: one call, or the rows
If you want the arithmetic done for you, the freight endpoint takes mass, distance and mode and returns the emissions with the factor, its source and the calculation shown: the Freight and Logistics Emissions API. The same operation is the calculate_freight tool on the MCP server. If you want the rows to run your own model, browse the keys above keyless and pin as_of to a data version so your calculator’s results reproduce after the next GLEC or DEFRA release. A worked example on this site: the rail freight calculator.
Frequently asked questions
GLEC Framework v3.2 default tonne-km factors for road, rail, sea and air, DEFRA’s delivery-vehicle and freight rows for UK fleets, and a carrier’s ISO 14083 declaration where you have one. GreenCalculus serves the first two by key with the source reference on every row, and a freight endpoint that returns emissions with the arithmetic shown.
No. ISO 14083 is the standard that sets the method and boundaries for transport-chain emissions; the GLEC Framework is the Smart Freight Centre’s guidance that applies it and publishes default factors. Version 3.2 of GLEC is aligned with ISO 14083, which is why a GLEC-based calculator is accepted in reports that cite the ISO standard.
The Smart Freight Centre publishes them for free use with attribution and states that the factor tables are reproducible; the corpus record on the GLEC explainer carries the ruling as read. DEFRA’s rows are Open Government Licence. Attribute both, and record the versions.
Because the unit is per tonne-kilometre and a container ship carries thousands of tonnes per voyage. The per-shipment figure can still be large once the distance is thousands of kilometres. Check the unit, the load assumption and the boundary before assuming the factor is wrong.