2-Stroke Premix Calculator
Calculate oil volume from fuel quantity and your chosen premix ratio.
Use the ratio specified by your engine builder, motorcycle manufacturer or oil recommendation. This calculator does not choose a ratio for you; it converts a ratio you already intend to use into ounces and milliliters of oil.
Premix ratio means parts fuel to one part oil. At 40:1, forty equal parts of gasoline use one equal part of oil. The arithmetic is simple, but a calculator helps avoid mental-math mistakes at the fuel jug.
How to use this tool
Enter the amount of gasoline you are actually mixing, then enter the fuel-to-oil ratio you have already selected from the motorcycle, engine builder or oil guidance. The calculator converts that ratio to fluid ounces and milliliters of oil.
Mix in a clean approved fuel container. Add a measured amount of oil and fuel using the procedure appropriate for your product, close the container and mix thoroughly. Label the jug when more than one fuel type or ratio is present in the pit.
Worked example
Five U.S. gallons at 40:1 requires 16.00 fluid ounces of oil, about 473 mL. That arithmetic is 5 × 128 ÷ 40. The tool is useful because it applies the same calculation to partial gallons and less convenient ratios.
Using it at the track
Use the calculator when filling a known-volume jug or when topping up with an awkward quantity such as 2.7 gallons. Enter the actual fuel amount rather than the container’s nominal capacity. If you add more gasoline later, calculate the oil needed for that additional fuel instead of guessing from the final jug level.
Keep one ratio per labeled container when possible. Mixing leftover fuel of an unknown ratio with fresh fuel creates uncertainty the calculator cannot resolve. If you do not know what is already in the jug, start with a clean, known mixture.
Before using the result
- Measure fuel and oil with containers you trust.
- Do not change premix ratio as a substitute for carburetor/fuel-injection tuning.
- If fuel quantity changes after mixing, recalculate rather than guessing.
Limit: This tool only converts quantities. It cannot determine whether 32:1, 40:1, 50:1 or another ratio is correct for a particular engine, oil, tune or riding use.