Precision Tuning Tool

E85 Calculator: Hit Your Target Ethanol Blend Every Time.

Stop guessing at the pump. Calculate the exact E85 and gas mixture for your E30, E50, or custom tune.

Verified Formula
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E85 Mixing Calculator

%
E?
typ. 10%
Advanced Settings (Pump Content)

Add This E85

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Gallons

Add This Gas

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Gallons

Final Blend: E30
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How E85 Mixing Works

3-step infographic showing how to mix E85 and gasoline to reach target ethanol blend
The E85 mixing process: Add fuel, blend in tank, hit your target.

Mixing E85 with regular gasoline allows you to create custom ethanol blends like E30 or E50. This is essential for performance tuners who need a specific octane level that their ECU tune is calibrated for. According to the U.S. Department of Energy, E85 contains 51-83% ethanol depending on the season.

Our calculator handles the math so you don't have to. Just enter your tank size, current fuel level, and target ethanol percentage, and we'll tell you exactly how many gallons of E85 and gas to add. Learn more about the science behind E85 mixing or check if your car is E85 compatible.

Frequently Asked Questions

What is E85 fuel?

E85 is a fuel blend containing 51% to 85% ethanol mixed with gasoline. It's used in Flex-Fuel vehicles and by performance enthusiasts for its high octane rating.

How accurate is this E85 calculator?

Our calculator uses the standard weighted average formula for mixing liquids. Results are highly accurate when you input the correct ethanol percentages for your pump fuels.

Can any car run E85?

No. Only Flex-Fuel vehicles or cars with aftermarket E85 conversion kits can safely run E85. Using E85 in a non-compatible car can damage fuel lines and the engine. Check our compatibility guide.

Calculator formula verified against SAE International standards for ethanol fuel mixing.

Last updated: December 2025 • Used by thousands of performance tuners worldwide