About this tool
The 2-Stroke Fuel/Oil Mix Calculator tells you precisely how much two-stroke oil to pour into a given amount of fuel to hit a target premix ratio. Two-stroke engines — chainsaws, string trimmers, dirt bikes, outboards, and older scooters — burn oil mixed into the gasoline to lubricate the crankcase, so getting the ratio right protects the engine from seizing (too little oil) or fouling plugs and smoking (too much oil).
For a ratio of R:1 and a fuel volume V, the oil quantity is simply Oil = V / R. Working in consistent units: for US gallons, oil (fl oz) = gallons × 128 / R; for litres, oil (ml) = litres × 1000 / R. This tool converts your fuel volume to millilitres internally, divides by the ratio, and reports the oil dose in both ml and fluid ounces, plus the total volume of the finished mix. Preset buttons cover the common ratios (16:1, 24:1, 32:1, 40:1, 50:1, 100:1) and a custom field handles anything in between.
Everything runs in your browser with no uploads. Always use the ratio and oil type specified in your equipment's manual — modern engines designed for 50:1 should not be run on a rich 32:1 mix and vice versa, and only use oil rated for air-cooled two-stroke engines (JASO FB/FD or ISO-L-EGD). Mix fresh fuel and shake the container well before filling the tank.