Question 1

How are freight CO₂ emissions calculated?

Accepted Answer

Freight emissions are calculated by multiplying three values: the weight of your cargo in tonnes, the distance travelled in kilometres, and an emission factor specific to the transport mode. The emission factor represents the kilograms of CO₂ equivalent produced per tonne of cargo per kilometre. This calculator uses well-to-wheel (WTW) factors that include both fuel production and combustion emissions.

Question 2

What emission factors does this calculator use?

Accepted Answer

Ocean freight factors come from the IMO 4th GHG Study (2020) via the GLEC Framework v3. Road and rail factors come from the UK DESNZ/DEFRA Greenhouse Gas Conversion Factors 2024. Air freight factors also come from DEFRA 2024. All factors are well-to-wheel (WTW), meaning they include upstream fuel production emissions as well as direct combustion.

Question 3

How much CO₂ does a container ship emit per container?

Accepted Answer

A typical 40ft container shipped from Shanghai to Rotterdam (19,550 km) produces approximately 3,550 kg of CO₂e — roughly 3.6 tonnes. A 20ft container on the same route produces about 2,260 kg. Actual emissions vary by vessel size, speed, load factor, and routing. Larger vessels (8,000+ TEU) are more efficient per container than smaller feeder ships.

Question 4

Is air freight really that much worse than ocean freight?

Accepted Answer

Yes. Air freight produces roughly 50 to 100 times more CO₂ per tonne-km than ocean container shipping. A 1-tonne shipment from Shanghai to Europe by air produces approximately 12,000 kg of CO₂e, compared to about 160 kg by ocean. If radiative forcing is included (the additional climate impact of emissions at altitude), air freight's total climate impact is even higher.

Question 5

What is well-to-wheel (WTW) vs tank-to-wheel (TTW)?

Accepted Answer

Tank-to-wheel (TTW) counts only the emissions from burning fuel during transport — the exhaust from the ship, truck, or plane. Well-to-wheel (WTW) adds the upstream emissions from extracting, refining, and transporting the fuel before it reaches the vehicle. WTW gives a more complete picture and is the approach used by the GLEC Framework and ISO 14083. This calculator uses WTW factors.

Question 6

What is the GLEC Framework?

Accepted Answer

The Global Logistics Emissions Council (GLEC) Framework is the industry standard for calculating and reporting greenhouse gas emissions from logistics operations. Developed by Smart Freight Centre, it provides harmonised emission factors and methodology for road, rail, ocean, and air freight. It is aligned with ISO 14083 and recognised by the Science Based Targets initiative (SBTi) and the GHG Protocol.

Question 7

Does this calculator include radiative forcing for air freight?

Accepted Answer

By default, no. Radiative forcing accounts for the additional climate impact of aircraft emissions at high altitude, including contrails, water vapour, and nitrogen oxide effects. DEFRA recommends a 1.9x multiplier to capture these non-CO₂ effects. You can enable this in the advanced options — it approximately doubles the reported emissions for air freight.

Question 8

How can importers reduce their shipping carbon footprint?

Accepted Answer

The most impactful action is choosing ocean over air freight wherever possible — this alone can reduce emissions by 95% or more. Other strategies include consolidating shipments to improve load utilisation, choosing carriers with newer and more efficient vessels, optimising routing to reduce distances, and shifting road legs to rail where infrastructure allows. Tracking emissions per shipment over time helps identify the biggest opportunities.

Freight CO₂ Emissions Calculator

Data sources