# When a truck, ship or aircraft also carries other people's goods, how does the Scope 3 guidance split its fuel, and can I use chargeable weight?

Canonical: https://senseible.earth/answers/scope-3-fuel-allocation-mass-volume-or-chargeable-weight

The Greenhouse Gas (GHG) Protocol's Scope 3 guidance splits a shared vehicle's fuel by mass for road, air and rail and by volume for ships, unless better data show another limit. Dimensional or chargeable mass may replace mass only where data are available to prove it more suitable.

## The default limit for each mode

- The guide says companies should allocate by these default limiting factors, unless more accurate data are available to show that another factor is the limiting factor.
- Road: truck capacity is typically limited by mass, so mass-based allocation. Marine: vessel capacity is typically limited by volume, so volume-based allocation. Air: typically limited by mass. Rail: typically limited by mass.
- If several shipments are on one leg, distance should also be used as a means of allocation.
- If the data needed for allocation are not available or reliable because of the variety of goods in one vehicle, the guide says the distance-based method should be used instead.

## The formula

Allocated fuel use equals the total fuel consumed in litres times the mass or volume of your goods divided by the mass or volume of all goods transported. The printed text of the guide shows that fraction the other way up; the sensible reading is your share of the total. You then run the allocated litres through the fuel-based formula, which adds up each fuel's litres times its factor, plus electricity, plus refrigerant leakage.

## Dimensional and chargeable mass

The guide defines dimensional mass as a calculated mass that takes into account packaging volume as well as the actual mass of the goods, and chargeable mass as the higher value of the actual or the dimensional mass. It says companies may optionally substitute mass, or volume, with dimensional or chargeable mass where data are available to prove that the alternative method is more suitable.

## How it sits with the air freight page here

The air freight page here says to use actual gross weight from the air waybill and not the billed chargeable weight. That agrees with the guide's default, which is mass. The guide's option is narrower than it looks: it needs data that prove chargeable mass is the better measure, and it applies to splitting fuel between goods on one vehicle. Our reading is that a carrier calculator that uses billed weight by default has not shown that proof, so ask for the basis and the evidence.

## One van trip using 100 litres of diesel, bulky goods (example quantities)

- Trip emissions: 100 x 2.645 = 264.5 kilograms of carbon dioxide (CO2)
- Your goods: 300 kilograms actual, 800 kilograms chargeable. All goods on the van: 1,200 kilograms actual, 2,000 kilograms chargeable
- By actual mass: 300 / 1,200 = 25.0 percent, so 264.5 x 0.25 = 66.1 kilograms
- By chargeable mass: 800 / 2,000 = 40.0 percent, so 264.5 x 0.40 = 105.8 kilograms
- The chargeable basis gives 105.8 / 66.1 = 1.6 times the actual mass figure

The litres, weights and chargeable masses are example numbers. Adding the chargeable masses of all shipments to get the van total is our assumption, because the guide does not say how. 2.645 kilograms of CO2 per litre of diesel is Senseible's diesel factor, from the Intergovernmental Panel on Climate Change 2006 default with a density of 0.83.

## What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so fuel for your own vehicles shows up once uploaded. Carrier fuel totals and the weights and volumes on each consignment come from the carrier's papers, which you keep.

- [Part-load shipments on one truck](https://senseible.earth/answers/how-to-calculate-emissions-for-part-load-shipments)
- [Air freight: actual or chargeable weight](https://senseible.earth/answers/air-freight-actual-or-chargeable-weight)
- [Freight: Scope 3 category 4 or 9](https://senseible.earth/answers/is-freight-scope-3-category-4-or-9)
- [Free calculators](https://senseible.earth/calculators)

Sources: [GHG Protocol Technical Guidance for Calculating Scope 3 Emissions, Category 4 (fuel-based method, Formula 4.4)](https://ghgprotocol.org/sites/default/files/2022-12/Chapter4.pdf)

Last reviewed 2026-11-05. Rules are from the GHG Protocol's Scope 3 Technical Guidance. Ask your buyer or verifier which weight basis they accept before you change from actual mass.