Sustainable Aviation Fuel (SAF) Blend Emissions & Cost Calculator

Introduction to the SAF blend calculator

A sustainable aviation fuel (SAF) blend calculator is most useful when you want to see how a different blend share changes aviation emissions without rebuilding a spreadsheet from scratch. It treats SAF and conventional jet fuel as a mixed stream and lets you compare the result against an all-jet baseline.

This SAF blend calculator focuses on the planning trade-off aviation teams usually ask about first: if the SAF share goes up, how quickly do emissions fall and how much does the direct fuel bill move? By combining total fuel burn with emission factors and unit prices for each fuel, it returns the blended lifecycle emission factor, total CO₂, the percent reduction versus a 0% SAF baseline, and the fuel cost difference. That makes it useful for route studies, supplier comparisons, and early procurement conversations, even though it is not a substitute for formal reporting.

How to use the calculator for SAF blends

1. Enter total fuel burn in kilograms (kg) for the flight, route, or fleet period you want to test.
2. Enter the SAF blend fraction as a percentage from 0 to 100. Example: 20 means 20% SAF and 80% conventional fuel.
3. Provide emission factors in kg CO₂ per kg fuel for both conventional fuel and SAF. If possible, use values built on the same lifecycle boundary.
4. Provide unit costs in $/kg for both fuels so the model can estimate the direct purchase impact of the blend.
5. Select Calculate Emissions to see the weighted emission factor, total emissions, reduction versus baseline, and cost difference.

For SAF blend scenarios, a good workflow is to hold total fuel burn and blend percentage steady while changing only the SAF emission factor and SAF price. That makes it easier to compare HEFA, Fischer–Tropsch, alcohol-to-jet, or power-to-liquid pathways on the same operational demand. If you are building a budget or procurement memo, rerun the case with conservative, central, and aggressive assumptions so the spread in emissions and cost is visible at a glance.

Formulas used for SAF blend emissions and cost

The SAF blend calculator uses a straightforward weighted-average approach. Let F be total fuel burn in kg, b the SAF blend fraction as a decimal, e_j the conventional fuel emission factor, e_s the SAF emission factor, c_j the conventional fuel cost, and c_s the SAF cost. Because the blend is treated as a simple mass mix, the same SAF fraction drives both the emissions equation and the cost equation.

• Weighted emission factor: EF = b·e_s + (1 − b)·e_j
• Total emissions: E = F·EF
• Baseline emissions (0% SAF): E₀ = F·e_j
• Emission reduction (%): R = (E₀ − E) / E₀ × 100
• Blended fuel cost: C = F·(b·c_s + (1 − b)·c_j)
• Cost difference vs. baseline: ΔC = C − (F·c_j)

Two things matter most in this SAF blend calculator. First, the emissions reduction depends on both the gap between SAF and jet-fuel emission factors and the share of SAF in the blend. Second, the cost premium scales with fuel burn as well as the price gap, so a blend that looks manageable on a short sector can become expensive on a long-haul mission. Keeping those effects together is the point of the calculator.

Worked example: default SAF blend inputs

Using the default SAF blend calculator inputs, imagine a flight or planning period that burns 10,000 kg of fuel and uses a 20% SAF blend. With conventional jet fuel at 3.16 kg CO₂/kg and SAF at 0.50 kg CO₂/kg, the weighted factor drops because one-fifth of the total mass is carrying the lower lifecycle value.

• EF = 0.20×0.50 + 0.80×3.16 = 2.628 kg CO₂/kg
• Total emissions E = 10,000×2.628 = 26,280 kg CO₂
• Baseline E₀ = 10,000×3.16 = 31,600 kg CO₂
• Reduction R = (31,600 − 26,280) / 31,600 × 100 ≈ 16.8%

For costs, if conventional fuel is $0.80/kg and SAF is $1.50/kg, the same blend raises the direct fuel purchase bill because the SAF portion costs more per kilogram.

• Blended cost C = 10,000×(0.20×1.50 + 0.80×0.80) = $9,400
• Baseline cost = 10,000×0.80 = $8,000
• Cost difference ΔC = $9,400 − $8,000 = $1,400

This example shows the core SAF blend trade-off in one place: the blend reduces lifecycle emissions, but it also creates a premium that procurement, policy support, or supplier discounts may need to absorb. If a credit or contract discount narrows the SAF price gap, the emissions benefit can come with a much smaller budget impact.

Assumptions behind SAF blend estimates

SAF blend calculators inherit the assumptions behind the emission factors you feed them. A commonly cited combustion-related factor for conventional jet fuel is around 3.16 kg CO₂ per kg fuel, but lifecycle values can be higher once extraction, refining, and transport are included. SAF values can vary widely depending on feedstock, process energy, land-use effects, transport distance, and how co-products are allocated.

This calculator treats the blend as a mass-based mixture and assumes the same operational fuel burn regardless of blend. In practice, certified SAF is intended to work in existing aircraft, although density and energy-content differences can still matter at the edges. For a high-level screening estimate that is usually fine, but engineering-grade fuel planning needs a more detailed performance model.

How to interpret SAF blend results in practice

For SAF blend decisions, the weighted emission factor is the fastest number to compare because it compresses the mix into a single metric. Lower values are better. Total emissions then scale that factor by fuel burn, so two flights with the same blend can have very different absolute CO₂ totals if one mission is much larger than the other.

The emission reduction percentage is the number to quote against climate targets, while the fuel cost difference is the number to use for budgeting and contracting. A blend that looks attractive on a percentage basis may still demand a large budget on high-burn operations, whereas a modest blend across a large fleet can still avoid substantial absolute emissions. That is why this page keeps the arithmetic transparent instead of hiding it inside a single sustainability score.

Limitations of this SAF blend calculator

• CO₂ only: This SAF blend calculator does not include non-CO₂ effects such as contrails, NO_x, or soot.
• Single emission factor per fuel: Real SAF supply chains can involve multiple stages, seasonal changes, and regional variation.
• No uncertainty ranges: Results are point estimates; sensitivity analysis is strongly recommended.
• Cost scope: Only direct fuel purchase cost is modeled; infrastructure, contracting, certificates, and policy incentives are excluded unless you adjust the input prices yourself.
• Blend constraints: Regulatory and certification limits may restrict maximum blend levels for certain SAF pathways or aircraft programs.

After you run a SAF blend calculation, the key outputs are repeated in the table below so you can scan them quickly or copy them into notes, slides, or internal reports.

Background on SAF pathways, policy, and operating context

SAF blend results sit inside a broader supply-chain story. The Hydroprocessed Esters and Fatty Acids (HEFA) pathway is currently the most mature, converting waste lipids into jet-range hydrocarbons through hydrotreating and isomerization. Alcohol-to-jet routes ferment sugars into alcohols and then upgrade them into hydrocarbons. Fischer–Tropsch synthesis can turn municipal solid waste or biomass into syngas and then into liquid fuels. Power-to-liquid concepts combine captured carbon dioxide with green hydrogen to produce synthetic hydrocarbons. Each pathway has different energy requirements, feedstock constraints, and land-use questions, so the SAF label can hide very different lifecycle outcomes.

Policy also matters because blending mandates, tax credits, low-carbon fuel standards, and carbon pricing can narrow the gap between SAF and conventional jet fuel. Programs such as ReFuelEU and other national incentives are intended to accelerate supply, but the quality of the emissions claim still depends on transparent lifecycle data and credible certification. If the electricity mix is carbon intensive or the feedstock creates indirect land-use change, the real climate benefit can shrink.

When you interpret the calculator's output, remember that lifecycle assessments depend on assumptions about feedstock sourcing, transport distances, process efficiency, and co-product allocation. A simple sensitivity check is to rerun the calculator with low, central, and high SAF emission factors. If the economics or emissions story changes dramatically across that range, the decision deserves more detailed sourcing analysis before you commit.

Finally, SAF is only one lever in aviation decarbonization. Fleet renewal, operational efficiency, air traffic improvements, demand management, and future aircraft technologies also matter. This page keeps the focus on blend arithmetic so you can quantify the immediate emissions and cost implications of a SAF procurement choice before layering on other strategies.