Guide · Carbon
Freight CO₂e per leg: the ISO 14083 method, step by step.
Scope 3 transport emissions are increasingly audited. A defensible number comes from weight, distance and the right factor for each leg, not from a spend-based estimate.
ISO 14083 is the international standard for quantifying greenhouse-gas emissions from transport chains. The GLEC Framework from the Smart Freight Centre is the widely used method aligned with it. For road freight, the core calculation is activity-based: tonne-kilometres multiplied by an emission factor for the vehicle and fuel.
The formula
CO₂e for a leg = weight (t) × distance (km) × emission factor (kg CO₂e per tonne-km)
Worked example
2.4 t × 850 km × 0.082 kg CO₂e per tonne-km (an example factor for a heavy diesel commercial vehicle) = 167.3 kg CO₂e for the leg.
Example factors by vehicle class
| Vehicle class | Example factor (kg CO₂e / t-km) |
|---|---|
| ≤ 3.5 t small CV | 0.380 |
| ≤ 12 t medium CV | 0.140 |
| ≤ 30 t heavy CV | 0.082 |
| > 50 t tractor-trailer | 0.055 |
These are the example factors used in SCM for Manufacturers. For reporting, use the default factors published in the GLEC Framework or fuel-based factors from your own data, and state which you used.
Rules that make the number defensible
- Calculate per leg, not per shipment average.
- Use the actual vehicle class and fuel of that leg.
- Flag missing weights; never guess them.
- Credit part-loads: allocate emissions by each consignment’s share of the load.
- Report the method, the factors and their source.
Ways to reduce it
- Higher load factor and part-load consolidation (see load planning).
- Less empty running.
- Mode shift to rail for long, bulk lanes.
- Cleaner fuels and newer vehicle classes on high-volume lanes.
In SCM for Manufacturers, every leg is calculated as weight × distance × the factor for that vehicle’s class and fuel on the ISO 14083 / GLEC tonne-km method; missing weights are flagged; part-loads are credited against an all-full-truck baseline by carrier, plant and lane; and the report exports to the ESG report. Try the freight CO₂e calculator.
Questions
What is ISO 14083?
The international standard for quantifying and reporting greenhouse-gas emissions from transport chains, including road freight.
How is road freight CO₂e calculated?
Weight in tonnes × distance in km × an emission factor in kg CO₂e per tonne-km for the vehicle class and fuel, calculated per leg.
Is spend-based estimation acceptable?
It is a rough starting point. Activity-based calculation per leg is more accurate and more defensible in an audit.
See it on your own data. SCM for Manufacturers puts the plant gate, carriers, RDC stock, cold chain and OTIF on one control tower. Book a 30-minute working session with an engineer.