Race Fuel Blend Calculator

NEOCAT

Race Fuel Calculator

Ethanol blend calculator for motorsport applications

Units

Current Ethanol % in Tank %

Current Fuel Level (L)

Ethanol Content of E85 %

Target Ethanol in Tank %

ETHANOL TO ADD

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// how it works

The blending math, in plain terms

When you mix high-ethanol fuel (like E85) into a tank that already holds some ethanol, the calculator works out the volume of E85 needed so the whole tank lands on your target ethanol percentage. It assumes you're topping up an existing volume rather than draining and refilling.

// volume of E85 to add add = fuelLevel × (target − current) ÷ (e85 − target)

Current Ethanol % — what's already in the tank right now (e.g. 10% from pump gas).
Current Fuel Level — how much fuel is in the tank, in litres or gallons.
Ethanol Content of E85 — the actual ethanol % of the fuel you're adding. Real-world E85 varies seasonally, so set this to your measured value (often 70–85%).
Target Ethanol — the blend you want the tank to end up at.

Worked example: 40 L of fuel currently at 10% ethanol, adding E85 measured at 85%, targeting 30% → 40 × (30 − 10) ÷ (85 − 30) = 14.55 L of E85.

The metric/imperial toggle simply relabels the units — the math is a ratio, so enter litres for a litres answer, or gallons for a gallons answer. Always confirm critical fuel mixes with a proper ethanol content meter before running. This tool is provided as-is for estimation.

// also available

Prefer a native desktop app?

A tiny 1.6 MB Windows build — no installer, runs fully offline, and sits in your tray at the track.

Download for WindowsWin 10 / 11 · x86-64 · ~1.6 MB