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Octane Blend Calculator

Estimate the blended octane of two fuels from their volumes and octane ratings.

Updated April 13, 2026
Free online tool
Planning and research use

Why this page exists

Fuel-blend planning gets easier when the two source fuels and their octane ratings are turned into one weighted-average estimate instead of being guessed manually. This calculator helps visitors estimate blended octane from two source fuels.

Interactive tool

Run the estimate

Enter your numbers and read the result first, then use the sections below to understand what affects the outcome.

Calculator

Octane blend calculator

Estimate blended octane from the volumes and octane ratings of two source fuels.

Result

94.00 octane

Estimated blended octane based on a simple weighted average of the two fuel volumes and octane ratings entered.

Blended octane94.00

Total blended volume12.00 gallons

Fuel A used8.00 gallons at 91.0

Fuel B used4.00 gallons at 100.0

8.00 gallons of fuel A and 4.00 gallons of fuel B produce about 12.00 gallons total.
Using a weighted average of the octane ratings gives a blend estimate near 94.00 octane.
Use the result as a planning estimate only, because real fuel chemistry can differ from the simple weighted-average assumption.

This is a weighted-average planning estimate, not laboratory fuel analysis. Real blend behavior can vary with fuel chemistry and the exact products being mixed.

Planning note

Last updated April 13, 2026. Use this tool to compare scenarios and plan ahead, then confirm important details with the lender, employer, insurer, contractor, or other qualified provider involved in the final decision.

How it works

What the calculator is doing

Enter the volume and octane rating for fuel A and fuel B.

The calculator adds the volumes to estimate the total blend size.

It uses a weighted-average formula to estimate the blended octane.

Understanding your result

This is a planning estimate, not laboratory analysis. Real fuel chemistry can vary, so the result is best used for rough blend planning rather than exact certification.

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Examples

Ways people use this tool

Example scenarios help turn a quick estimate into a more useful comparison or planning step.

Estimate the octane of a two-fuel blend

A quick weighted-average estimate can make it easier to plan a mix of higher-octane and lower-octane fuel.

Compare two mix ratios

Changing the volume split can show how strongly the higher-octane fuel shifts the final blend estimate.

Use it with fuel-planning tools

Octane blend math often fits naturally beside premium-versus-regular and air-fuel-ratio checks.

FAQ

Common questions

How is blended octane estimated here?

The calculator uses a weighted average based on the two source volumes and their octane ratings.

Do the two fuels need to use the same volume unit?

Yes. Both source fuels need to use the same unit, such as gallons or liters, for the blend estimate to make sense.

Why is this only a planning estimate?

Because real fuel chemistry can vary, and a simple weighted average does not capture every detail of actual laboratory blend behavior.

Related tools

Keep comparing

Use these related tools to compare nearby scenarios, check a second estimate, or keep narrowing down the right decision.

Auto ToolsUpdated April 12, 2026