Two-stroke fuel mix calculator
Enter how much fuel you are mixing and the ratio your engine maker specifies, such as 50:1. The calculator tells you how much two-stroke oil to add, in millilitres and US fluid ounces. Always use the ratio and oil type given in your engine's manual.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose litres or US gallons.
- Enter the amount of fuel you will mix.
- Enter the ratio from your manual.
- Measure the oil with a graduated mixing bottle, then add the fuel and shake.
How it works
- Oil = fuel ÷ ratio.
- 1 US gallon = 3.785411784 L = 128 US fl oz; 1 US fl oz = 29.5735 mL.
- Finished mix = fuel + oil.
Worked example
5 litres of fuel at 50:1 needs 100 mL of oil, or 3.38 US fl oz, and gives 5.1 litres of mix. One US gallon at 40:1 needs 3.2 fl oz (94.6 mL).
Tips
- Follow the manual for ratio and oil specification.
- Pour the oil in first and then the fuel, and shake well.
- Mix only what you need; stored mix can degrade.
Frequently asked questions
How is the oil amount worked out?
Oil = fuel ÷ ratio, with both in the same unit. At 50:1, 5 litres of fuel needs 5 ÷ 50 = 0.1 litre, which is 100 mL. One US gallon at 40:1 needs 128 fl oz ÷ 40 = 3.2 fl oz.
What ratio should I use?
The one in your engine or equipment manual. Ratios from 25:1 to 100:1 are in use, depending on the engine and the oil. Do not guess; too little oil risks engine damage, too much causes smoke and deposits.
Do the fluid ounces mean US or UK?
US fluid ounces (29.5735 mL), matching the US gallon of 3.785 litres. A UK fluid ounce is slightly smaller, about 28.41 mL.
Does the ratio mean oil per fuel or per mix?
It is fuel to oil, as is standard: 50:1 means 50 parts fuel to 1 part oil. The finished mix is fuel plus oil, shown as a total.