Octane rating converter
Find the US pump octane that matches a European or Asian RON rating, or the other way round.
95 RON is posted as about 90.5 at a US or Canadian pump.
What it means
Where does that octane sit?
Approximate: the gap between RON and MON varies with the blend, typically 8 to 12 points. Use the grade your owner’s manual asks for.
Every unit
That petrol on every scale
Learn
Three things worth knowing
-
Add about 4 or 5
RON ≈ AKI + 4.5: 87 → 91.5, 91 → 95.5, 93 → 97.5.
-
Iso-octane = 100
Graham Edgar set the scale in 1926: heptane, which knocks badly, is 0; iso-octane, which resists, is 100.
-
95 in Europe is not 95 in the US
European 95 RON is the standard grade; 95 AKI in the US would be a racing fuel.
Shortcuts
Popular octane rating conversions
Background
About octane numbers
Octane measures how well petrol resists knocking. Two lab tests exist: the Research Octane Number (RON) and the harsher Motor Octane Number (MON). Most of the world posts RON at the pump; the US and Canada post their average, (R+M)/2, also called AKI.
That is why US numbers look lower: regular 87 AKI is about 91–92 RON, premium 91–93 AKI about 95–98 RON.