Mixing an ethanol target
Enter the fuel already in the tank and the measured ethanol content of both fuels. Pump “E85” is not always E85.
Fuel planning
Fuel & Ethanol Calculators
Mix ethanol or octane targets, estimate injector demand, convert lambda correctly, and understand the real cost of the fuel plan.
Decision guide
Start with the job you need to do
Sizing a fuel system
Use horsepower, BSFC, injector count, pressure assumptions, and a conservative duty-cycle ceiling.
Comparing operating cost
Calculate cost per mile rather than price per gallon so economy and energy-content differences are visible.
Calculators & references
Tools in this category
E85 Blend Calculator
Calculate the exact E85 and pump-gas amounts required for a target ethanol content.
Flex fuelOctane Blend Calculator
Calculate the octane of a fuel mix or the race-gas amount needed for a target.
Race fuelFuel Injector Sizing
Estimate the injector flow required for a power target using BSFC, duty cycle, and cylinder count.
Fuel systemAFR & Lambda
Convert AFR and lambda for gasoline, ethanol blends, methanol, and diesel.
TuningFuel Cost Calculator
Compare cost per mile, monthly fuel expense, and annual spend between vehicles or fuels.
OwnershipFuel math is only as good as the measured inputs
A label on the pump is not a laboratory measurement. Ethanol content can vary by season and supplier, and the fuel already in the tank is rarely known perfectly. The blend calculator lets you replace optimistic assumptions with an ethanol-content test and an honest estimate of current tank volume.
Injector sizing has the same dependency on assumptions. Brake-specific fuel consumption changes with engine design, fuel, enrichment, and efficiency. Injector flow also depends on differential fuel pressure. The calculator is most useful when it exposes these inputs and leaves headroom, not when it produces one seemingly exact part number.
For tuning work, lambda is the cleanest way to compare mixtures across fuels. AFR displays depend on the stoichiometric reference selected by the logger or gauge. Always confirm how a device reports mixture before treating an AFR number as gasoline-equivalent or fuel-specific.
Methodology and responsibility
Formulas, assumptions, and limitations are shown on the individual tool pages. TunerBench is maintained as an educational planning resource. Verify safety-critical specifications with the vehicle or component manufacturer and the professional responsible for the work.
Reviewed August 11, 2026 · How TunerBench verifies calculations · Report an issue
Common questions
Is pump E85 always 85% ethanol?
No. The actual content varies seasonally and geographically. Test the fuel when the blend matters to the calibration.
Is octane blending perfectly linear?
The simple calculator uses a volume-weighted estimate. Real fuel blending can be nonlinear, so verify critical race-fuel combinations with the supplier.
Why use lambda instead of AFR?
Lambda expresses mixture relative to stoichiometric regardless of fuel. AFR depends on the stoichiometric value assumed by the display or logger.
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