Octane Mixing Calculator

Blend two fuels to get the resulting octane — or the ratio to hit a target.


Reverse: hit a target octane

How it works

1

Enter both fuels

Octane (RON) and volume of each fuel you are mixing.

2

Blend

The result is the volume-weighted octane of the mix.

3

Or target

Enter a target octane and tank size to get how much of each fuel to add.

Frequently asked questions

How do you calculate blended octane?

As a volume-weighted average: (octaneAxvolA + octaneBxvolB) ÷ (volA+volB). It is a close approximation; real blending can be slightly non-linear, especially with oxygenates like ethanol.

Can I mix 95 and 98?

Yes — mixing equal parts 95 and 98 gives about 96.5 RON. The calculator shows the exact figure for any ratio.

Does E85 raise octane?

Ethanol has a high effective octane (~104–108 RON), so adding E85 raises the blend octane — but it also leans the mixture, so fuelling must support it.

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