2-Stroke Oil Mix Calculator
How much two-stroke oil to add to your petrol — for 50:1, 40:1, 32:1, 25:1, 100:1 or any ratio, in ml or fl oz.
Always use the mixing ratio in your engine’s manual and two-stroke oil made for that type of engine. Too little oil can damage the engine.
About this tool
Enter how much petrol you have and the mixing ratio from your engine’s manual, and get exactly how much two-stroke oil to add — for chainsaws, trimmers, leaf blowers, mopeds and outboard motors. Works in litres and millilitres or in US gallons and fluid ounces, and shows the oil per litre or gallon so you can mix any amount.
Frequently asked questions
100 ml. At 50:1 you add 1 part oil to 50 parts petrol, which is 20 ml of oil per litre: 5,000 ml ÷ 50 = 100 ml. For 1 litre that is 20 ml, for 2 litres 40 ml and for 10 litres 200 ml.
Fifty parts petrol to one part two-stroke oil, so the oil is 2% of the petrol volume. 40:1 is 2.5%, 32:1 about 3.1% and 25:1 is 4%. The lower the number, the more oil. In Norway and some other countries the same ratio is written 1:50.
A US gallon is 128 fl oz, so 50:1 needs 128 ÷ 50 = 2.56 fl oz of oil per gallon (about 76 ml). 40:1 needs 3.2 fl oz, 32:1 needs 4 fl oz and 25:1 needs 5.12 fl oz per gallon.
Always the one in your engine’s manual — many modern garden tools use 50:1, while older or other engines may need more oil. Too little oil can damage the engine through poor lubrication; too much gives more smoke and deposits. Use two-stroke oil made for your type of engine and shake the can before filling.
Related tools
Volume ConverterConvert gallons to litres, litres to cubic metres, cubic feet, pints, quarts and more — US and UK units.Fuel Cost CalculatorWork out what a car trip will cost in fuel — and split it between passengers.Ratio CalculatorSolve a proportion A : B = C : ? and simplify a ratio to its lowest terms.Fuel Economy ConverterConvert fuel consumption between L/100 km, litres per mil, km/L and US or UK miles per gallon.Firewood Energy CalculatorHow many kWh of heat you get from firewood — by sacks or weight, moisture content and stove efficiency — and what the same heat costs as electricity.