GLEC v3.2 in Practice: Three Worked Freight Emission Calculations
Freight emissions are not hard to calculate. The formula has three inputs and one division. What makes it feel complicated is the table of emission factors, the alphabet soup of WTW/TTW/WTT, and the fact that everyone quotes the number in different units. I'm going to walk through three shipments — sea, road, and air — using GLEC Framework v3.2 defaults, and show the whole working. If you follow the first example, the other two are the same thing with different numbers.
The formula, such as it is
Every freight emission calculation aligned with ISO 14083:2023 and GLEC Framework v3.2 boils down to:
Emissions (kg CO2e) = Distance (km) × Mass (tonnes) × Emission Factor (g CO2e per tonne-km) ÷ 1,000
That's the whole thing. The reason the formula lives inside a 200-page standard is that the three inputs all need caveats. "Distance" must be the great-circle or actual-routed distance depending on the mode. "Mass" must be in tonnes, including packaging, and for roll-on/roll-off or container traffic you sometimes have to allocate on TEU or lane-metre basis instead. "Emission factor" needs to be well-to-wake (WTW), meaning it includes both the CO2 from burning the fuel (tank-to-wake, TTW) and the upstream emissions from producing the fuel (well-to-tank, WTT). CSRD Scope 3 reporting and ISO 14083 both require the WTW figure. I'll use WTW throughout.
Example 1: Shanghai to Rotterdam by container ship
A 40-foot container loaded with 20 tonnes of cargo sails from Shanghai to Rotterdam via the Suez Canal. The routed distance is about 19,600 km. GLEC v3.2 gives a default WTW emission factor for "container ship, average fleet" of roughly 8.15 g CO2e per tonne-km. Plug the numbers in:
19,600 × 20 × 8.15 = 3,194,800 grams CO2e, or about 3,195 kg CO2e for the whole shipment. That's in the region of a single passenger car's full-year footprint, burned on one voyage of one box on one ship. Container shipping is remarkably efficient per tonne-kilometre — it's the intercontinental distances that make the absolute numbers large.
If you want to split the figure for Scope 1 and Scope 3 reporting, the TTW share for marine distillate at this factor is about 6.3 g/tkm and the WTT share is about 1.85 g/tkm. That split varies slightly by fuel and engine, but those two components always add up to the WTW total.
Example 2: Munich to Milan by articulated truck
Twelve tonnes of cargo loaded on an articulated truck (gross combined weight above 32 tonnes), running from Munich to Milan via the Brenner Pass. Routed distance: 490 km. GLEC v3.2 gives a default WTW factor of about 62 g CO2e per tonne-km for a fully loaded articulated truck in this weight class on European motorways.
490 × 12 × 62 = 364,560 g, or about 365 kg CO2e. Notice what just happened: road freight has a per-tonne-km emission factor roughly 7.6 times higher than container shipping, but the short distance keeps the total lower than Shanghai-Rotterdam. This is exactly why the mode-versus-distance tradeoff matters so much in modal shift decisions — the factor ratio dominates on long hauls, and the distance ratio dominates on short ones.
One thing the default factor hides: empty running. The GLEC table assumes a sector-average 25% empty mileage. If your carrier tells you their dedicated lane runs at 10% empty (well-managed retail backhaul networks can get close to that), the real per-tonne-km figure is noticeably lower. That's a legitimate Tier 2 adjustment, but only if you have audited data to support it. Don't guess.
Example 3: Los Angeles to Tokyo by air
Half a tonne (500 kg) of high-value cargo moves in the belly hold of a passenger flight from LAX to Narita, great-circle distance about 8,770 km. GLEC v3.2 gives a default WTW factor for long-haul belly cargo of about 608 g CO2e per tonne-km. The belly-cargo factor is calculated with a mass-based allocation between passengers and freight, which is the ISO 14083 default.
8,770 × 0.5 × 608 = 2,666,080 g, or about 2,666 kg CO2e. Half a tonne by air produced nearly as much CO2e as twenty tonnes by sea on the first example. The air freight factor is roughly 75 times higher than container shipping per tonne-km. If you ever find yourself debating whether to air-freight a small order of parts to avoid stock-out, that ratio is the one to keep in your head — the calculation almost always comes out against the air option on emissions alone.
A quick honest caveat: the belly-cargo factor specifically does not include radiative forcing. Aviation's climate impact is larger than the CO2-only number suggests, by a factor that IPCC AR6 puts somewhere between 1.7x and 3x depending on altitude and contrail conditions. Most CSRD disclosures still report CO2e only because the radiative-forcing multiplier is methodologically unsettled. Mention it in your footnotes and move on.
Where defaults stop being good enough
Everything above uses GLEC's Tier 1 default factors. That's the starting point and it's fine for most reporting — including CSRD — if you disclose it as a default. The data quality tier nomenclature comes from ISO 14083:2023. Tier 2 is modelled data: carrier-specific fleet averages, vessel-IMO-number matching for a named ship on a named voyage, or route-adjusted factors derived from the carrier's own fuel consumption. Tier 3 is primary data, meaning actual metered fuel burn on the specific trip you're reporting. Each step up gives you a more accurate number, at the cost of needing better data from your carriers.
In practice, most operators I work with start at Tier 1 for every mode, upgrade ocean legs to Tier 2 when they consolidate with a single carrier on a regular trade lane, and only get to Tier 3 on road legs where they control the fleet. That's fine. The ISO 14083 standard explicitly allows mixing tiers within a single shipment — what it requires is that you declare which tier you used for each leg.
Where this can go wrong
Three common mistakes I see, roughly in order of frequency:
Using TTW instead of WTW. The TTW number is smaller and tempting. It's also wrong for Scope 3. CSRD disclosure and GLEC reporting both require WTW. If you ever see a factor quoted without the WTW/TTW label, assume TTW and add roughly 15-25% to get to WTW for marine fuels, or look up the specific factor in the GLEC tables.
Using straight-line distance for road and ocean. Great-circle distance is appropriate for air and sometimes for deep-sea ocean, but short-sea and road have to use routed distance. The Munich-Milan great-circle is about 350 km; the routed distance is 490 km. That's a 40% understatement if you pick the wrong one.
Double-counting the backhaul. If the carrier tells you their per-tonne-km factor already reflects empty running (GLEC defaults do), don't then apply your own 1.3x multiplier for "the truck has to come back." That backhaul is already in the factor. It's surprisingly common to see it added twice.
One more thing
If you want to build a sanity check into your reporting, here's a rough rule of thumb I keep on a sticky note: container shipping is around 8 g/tkm WTW, rail is around 20 g/tkm, road is around 60-80 g/tkm, and air is around 500-900 g/tkm. If a number you've just calculated is wildly outside those ranges per tonne-kilometre, something in the formula is wrong before the auditor tells you so.
The Tier 1 vs Tier 2 boundary I’m honest about
Every worked example above is Tier 1 — modelled defaults, no audited fuel burn. We default to Tier 1 for any shipment without carrier-supplied per-trip fuel data, because the alternative is to silently mix tier sources inside a single disclosure and that is the audit finding I dread the most. A Tier 2 upgrade on the sea leg requires the vessel IMO number plus carrier-published fleet-average bunker consumption; a Tier 3 upgrade on the road leg requires the carrier’s telematics feed for the specific trip. We can do either, but only when the underlying data is real. Where you see Tier 1 in the calculator output, take it at face value — that is what the data we have supports today.
Sources
GLEC Framework v3.2, Smart Freight Centre, 2023 — default emission factors for container ship fleet average, articulated truck >32t, and long-haul belly cargo. ISO 14083:2023 — Quantification and reporting of greenhouse gas emissions arising from transport chain operations. IPCC AR6 Working Group III, Chapter 10 (Transport), for the non-CO2 aviation radiative-forcing factor range. All three worked examples use published default factors as of the GLEC v3.2 revision and are reproducible from the tables in that document.
The EcoFreight calculator uses these same factors end-to-end; you can enter a multi-leg shipment and get the WTW/TTW/WTT breakdown per leg. The same formulas drive every response from the freight emissions API. For the regulatory context on why CSRD auditors care about the WTW number specifically, see the 2026 compliance checklist.