What is a tonne-kilometre?

A tonne-kilometre is one tonne of cargo moved one kilometre. It is the standard freight activity unit because emissions scale with both how heavy a load is and how far it travels. Multiplying tonnes by kilometres gives the activity, which is then multiplied by an emission factor.

Where do the emission factors come from?

The defaults are representative well-to-wheel values aligned with the GLEC Framework and similar logistics inventories: road around 62, rail around 22, sea around 8, and air around 602 grams CO2e per tonne-km. Real factors vary by vehicle, fuel, and load factor, so the tool lets you override the figure.

Why is air freight so much worse than sea?

Air freight emits roughly seventy times more CO2e per tonne-km than sea freight because aircraft burn large amounts of fuel to stay aloft and carry comparatively little cargo. Shifting even part of a shipment from air to sea or rail is the single largest lever for cutting freight emissions.

How is the offset cost calculated?

The tool converts total emissions to tonnes of CO2e and multiplies by the carbon price you enter, in your currency per tonne. Voluntary offset prices commonly range from a few dollars to over fifty per tonne depending on project quality and permanence.

Is an offset the same as reducing emissions?

No. Offsets compensate for emissions you could not avoid by funding reductions elsewhere; they do not eliminate the original emissions. Best practice is to cut footprint first through mode shift, load consolidation, and routing, then offset the residual.

What is the Freight Carbon Footprint & Offset Calculator?

Apply GLEC-aligned emission factors by transport mode (grams CO2e per tonne-km) to shipment weight and distance to estimate a freight carbon footprint, then price an offset at your chosen carbon price. For sustainability teams and shippers reporting scope 3 logistics emissions. It runs free in your browser on Gera Tools, with nothing uploaded.

Freight Carbon Footprint & Offset Calculator

Name: Freight Carbon Footprint & Offset Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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Every shipment has a carbon footprint that scales with how heavy it is and how far it travels. This calculator multiplies your freight activity in tonne- kilometres by a mode-specific emission factor to estimate CO2e, then prices an offset at your chosen carbon price for scope 3 logistics reporting.

How it works

The core formula is a single multiplication, repeated per leg:

activity (tonne-km) = weight (tonnes) x distance (km)
emissions (g CO2e)  = activity x emission factor (g CO2e per tonne-km)
emissions (t CO2e)  = emissions (g) / 1,000,000
offset cost         = emissions (t) x carbon price (per tonne)

The default emission factors are representative well-to-wheel values aligned with the GLEC Framework. Road is roughly 62, rail 22, sea 8, and air 602 grams CO2e per tonne-km. Because real intensity depends on vehicle type, fuel, and how full the vehicle runs, the factor is editable.

Example

A 10 tonne shipment moved 800 km by road is 8,000 tonne-km. At 62 g CO2e per tonne-km that is 496,000 g, or 0.496 t CO2e. At a 30 per tonne carbon price the offset costs about 14.88.

Using tonne-km data for Scope 3 logistics reporting

Under the GHG Protocol’s Scope 3 Standard, Category 4 (upstream transportation) and Category 9 (downstream transportation) require companies to report the emissions from freight they purchase. The recommended method for logistics is the spend-based or distance-and-weight-based approach, with the latter (this calculator’s method) considered more accurate because it reflects actual freight activity rather than just cost.

For an annual Scope 3 report, you would aggregate tonne-km data across all shipment legs for the year by mode, apply the appropriate emission factor, and sum to a total. If your 3PL or freight forwarder provides tonne-km data in invoices or sustainability reports, use those directly. If not, estimate from weight and distance for each major lane.

Mode shift: the single highest-leverage intervention

Relative to other decarbonisation levers, mode shift is extraordinary in its impact-to-cost ratio:

Air to sea: reduces per-tonne-km emissions by approximately 98–99%. A 10 tonne shipment moved 8,000 km by air generates over 48 t CO2e; the same shipment by sea generates under 1 t CO2e.
Road to rail: reduces emissions by roughly two-thirds in most geographies. This is the most accessible mode shift in many supply chains where rail freight corridors exist.
Road consolidation: combining partial loads into a full truck load (FTL) rather than shipping less-than-truckload (LTL) can cut per-tonne-km emissions by 20–40% simply by improving vehicle utilisation, with no mode change required.

The carbon price for offsetting residual emissions typically ranges from a few dollars per tonne for forestry avoidance credits to $50–150+ per tonne for high-quality removal credits (biochar, enhanced weathering). This cost is tiny relative to freight costs but grows linearly with the emissions you choose not to reduce.

Notes

Mode shift dominates everything else: moving the same shipment by rail instead of road cuts emissions by roughly two-thirds, and switching air to sea cuts them by over ninety-five percent. Reduce first, then offset the residual. Emission factors are representative GLEC-aligned well-to-wheel averages; actual factors depend on vehicle type, fuel, and load factor. For formal reporting, use primary data from your carrier where available.