“How many SAF certificates do I need?” has a simple formula and one trap. The formula is your flight emissions times the share you address, divided by what one tonne of SAF saves. The trap is that SAF certificates are counted in tonnes of fuel, while your footprint is in tonnes of CO2e, and the conversion depends on how the fuel was made.
This article walks through the calculation in the same order we use with clients, with a worked example and ambition levels you can copy.
The short answer. SAF certificates needed (tonnes of fuel) = flight emissions (tCO2e) × the share you address ÷ tCO2e avoided per tonne of SAF. For HEFA from used cooking oil, that last number is about 3.3.
Start from your flight footprint
Your flight footprint is both the starting point and the ceiling. Under the RSB Book & Claim Manual (version 4.2, effective since 3 December 2025), a company cannot claim more SAF than its total air travel and air freight footprint in the reporting year. SBTi’s Corporate Net-Zero Standard V2.0 applies the same idea through its volume matching criterion.
Include business travel (Scope 3 Category 6) and, if you pay for air freight, Categories 4 and 9. Use one consistent set of emission factors. The UK government’s 2026 conversion factors are widely used: 0.33940 kg CO2e per passenger-kilometre for long-haul business class and 0.11704 kg for long-haul economy, both including radiative forcing, the extra warming from non-CO2 effects of flying.
Decide whether you count radiative forcing and stick to it. In the UK factors it adds about 70% to long-haul flight emissions compared with the same factors without it, so it changes both your footprint and the maximum you can claim.
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Reduction factor per pathway
A SAF certificate represents one tonne of neat SAF. How many tonnes of CO2e that tonne avoids depends on the pathway’s life cycle emissions compared with fossil jet fuel. ICAO publishes default life cycle values per pathway against a fossil baseline of 89 gCO2e/MJ (November 2025 edition).
To convert, multiply the saving per megajoule by the energy in one tonne of fuel. We use 44 MJ per kg, the EU Renewable Energy Directive value for HEFA and Fischer-Tropsch jet fuel, for every pathway to keep the comparison simple.
Pathway (ICAO default value) | Life cycle emissions | Reduction vs fossil | tCO2e avoided per tonne of SAF |
|---|---|---|---|
HEFA, used cooking oil | 13.9 gCO2e/MJ | about 84% | about 3.3 |
HEFA, tallow (batches until 2029) | 22.5 gCO2e/MJ | about 75% | about 2.9 |
Fischer-Tropsch, forestry residues | 8.3 gCO2e/MJ | about 91% | about 3.6 |
Alcohol-to-jet, agricultural residues (integrated) | 24.6 gCO2e/MJ | about 72% | about 2.8 |
Alcohol-to-jet, sugarcane ethanol | 32.8 gCO2e/MJ | about 63% | about 2.5 |
Alcohol-to-jet, US corn ethanol | 72.4 gCO2e/MJ | about 19% | about 0.7 |
Power-to-liquid has no ICAO default value; its reduction is calculated per plant. Always use the life cycle value on your retirement statement for the final number, because it can differ from the default. For what each pathway means for price and availability, see the best SAF certificates to buy in 2027.
The spread matters more than most buyers expect. The same 100 tCO2e target needs about 30 tonnes of used-cooking-oil SAF, but about 140 tonnes of corn-based alcohol-to-jet.
A worked example
An illustrative company, with hypothetical numbers: 1,000 tCO2e of flight emissions in 2027, all business travel, calculated with radiative forcing. It buys SAF certificates from used-cooking-oil HEFA at about 3.3 tCO2e per tonne.
Step | Calculation | Result |
|---|---|---|
Flight footprint 2027 | from travel data | 1,000 tCO2e |
Share addressed with SAF | 10% | 100 tCO2e |
Reduction per tonne of SAF | ICAO default, used cooking oil | about 3.3 tCO2e |
SAF certificates needed | 100 ÷ 3.3 | about 30 tonnes |
Ceiling check | 100 tCO2e ≤ 1,000 tCO2e | within the RSB limit |
The remaining 900 tCO2e is still in the company’s inventory. If it wants to address those emissions too, carbon credits are the tool, sized from the same footprint so no tonne is counted twice. Our comparison of SAF certificates vs carbon credits explains how to report the two side by side. Our guide on how many carbon credits you need uses the same year-by-year logic for credits.
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Ambition levels
There is no rule for what share of flight emissions to address with SAF. The table shows three common starting points for the example company, with the volume in tonnes of used-cooking-oil SAF.
Ambition | Share of flight emissions | tCO2e addressed | SAF certificates (UCO HEFA) | Indicative cost at $150 to $500 per tCO2e |
|---|---|---|---|---|
Pilot | 5% | 50 | about 15 tonnes | $7,500 to $25,000 |
Commitment | 10% | 100 | about 30 tonnes | $15,000 to $50,000 |
Leadership | 20% | 200 | about 61 tonnes | $30,000 to $100,000 |
The price range is indicative, based on public figures from Patch (July 2026) and a SABA buyers’ tender (May 2025). SAF certificate prices vary by pathway, certification, vintage and volume; see SAF certificate prices in 2026 for what drives a quote, and our guide to a carbon credit budget for 2027 for the wider budget.
For context, ReFuelEU Aviation requires fuel suppliers at EU airports to blend at least 2% SAF since 2025, 6% from 2030 and 20% from 2035 (Regulation (EU) 2023/2405). A voluntary share above the mandate is easier to explain as your own contribution.
Tip from Bernard de Wit, Co-founder of Regreener: “Pick the share you can fund again next year, not the one that looks best in this year’s report. SAF supply is tight and prices move, so a pilot of 5% that grows to 10% and then 20%, with delivery periods agreed per year, is a stronger commitment to your board and your auditor than a one-off 20% you cannot repeat.”
Building up over multiple years
SBTi V2 recommends acquiring market instruments progressively, and supply is easier to secure with a plan than with one-off purchases. A simple build-up for the example company, assuming its flight footprint falls 5% a year through a stricter travel policy:
Year | Flight footprint (hypothetical) | Share with SAF | tCO2e addressed | SAF certificates (UCO HEFA) |
|---|---|---|---|---|
2027 | 1,000 tCO2e | 5% | 50 | about 15 t |
2028 | 950 tCO2e | 10% | 95 | about 29 t |
2029 | 900 tCO2e | 15% | 135 | about 41 t |
2030 | 860 tCO2e | 20% | 172 | about 52 t |
Two things stand out. The volume of SAF rises even though the footprint falls, because the share grows. And each year needs its own retirement statement in the right reporting year, so a multi-year agreement should fix delivery periods, not only volumes. SBTi V2 is usable for target validation from 1 February 2027 and mandatory for new submissions from 1 February 2028, which makes 2027 a natural first year for companies setting new targets; our SBTi V2 overview explains the transition.
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A volume per year, a pathway mix and a budget, sized together with the carbon credits for your residual emissions.
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Size SAF and carbon credits together
The SAF volume is one part of the plan; the residual emissions are the other. Regreener sizes both from the same flight footprint, sources SAF certificates supplier-agnostically from recognised certification schemes and registries, and adds carbon credits that pass our 100+ datapoint quality framework. For the purchase steps, read how to buy SAF certificates; for the reporting, how to report SAF certificates in Scope 3. To choose who to buy from, see 5 partners to source SAF certificates from in 2027. If you want the calculation done for your own data, talk to a SAF specialist.
