Calculate the exact amount of oil needed for your fuel gas mixture.
Gallons (US)
Liters
Gallons (UK/Imperial)
25:1 (Old Outboards/Saws)
32:1 (Classic Motocross)
40:1 (Standard Power Tools)
50:1 (Modern Stihl/Husqvarna)
100:1 (Amsoil/Specialty)
Custom Ratio
Required Oil Amount:
Understanding 2-Stroke Fuel Ratios
A 2-stroke engine (commonly found in chainsaws, weed whackers, and dirt bikes) requires a mixture of gasoline and specialized 2-stroke oil. Unlike a 4-stroke engine with a separate oil reservoir, the 2-stroke engine relies on the oil mixed into the fuel for lubrication of the piston and crankshaft.
Common 2-Stroke Ratios
Ratio
Typical Application
Oil per Gallon (US)
25:1
Older vintage equipment
5.12 fl oz
32:1
High-performance racing bikes
4.0 fl oz
40:1
Most modern lawn equipment
3.2 fl oz
50:1
Modern Stihl & Husqvarna products
2.6 fl oz
How to Use This Calculator
To get the perfect mix, follow these three steps:
Identify your Ratio: Check the fuel cap or the owner's manual of your equipment. 50:1 and 40:1 are the most common modern standards.
Measure your Fuel: Enter the exact amount of gasoline you have in your gas can.
Mix: Our calculator will tell you exactly how many Ounces or Milliliters of oil to add. Always add the oil to the gas can first, then add the fuel to ensure a thorough mix.
Example Calculation (50:1 Ratio)
If you have 5 Gallons of gasoline and your manufacturer specifies a 50:1 ratio:
Convert gallons to ounces: 5 x 128 = 640 ounces.
Divide by ratio: 640 / 50 = 12.8 ounces.
Result: You need 12.8 fluid ounces of 2-stroke oil.
Critical Safety Tips
Never use automotive motor oil in a 2-stroke engine. Always use oil specifically labeled as "2-Cycle" or "2-Stroke" oil. Using the wrong ratio can lead to "running lean" (too little oil, which causes engine seizure) or "running rich" (too much oil, which causes spark plug fouling and heavy smoke).
var ratioSelect = document.getElementById("ratioPart");
var customContainer = document.getElementById("customRatioContainer");
ratioSelect.onchange = function() {
if (this.value === "custom") {
customContainer.style.display = "block";
} else {
customContainer.style.display = "none";
}
};
function calculateMix() {
var fuelAmount = parseFloat(document.getElementById("fuelAmount").value);
var fuelUnit = document.getElementById("fuelUnit").value;
var ratioType = document.getElementById("ratioPart").value;
var ratioValue;
if (ratioType === "custom") {
ratioValue = parseFloat(document.getElementById("customRatio").value);
} else {
ratioValue = parseFloat(ratioType);
}
if (isNaN(fuelAmount) || fuelAmount <= 0) {
alert("Please enter a valid fuel amount.");
return;
}
if (isNaN(ratioValue) || ratioValue <= 0) {
alert("Please enter a valid ratio number.");
return;
}
var resultDisplay = document.getElementById("mixResult");
var primaryRes = document.getElementById("primaryResult");
var secondaryRes = document.getElementById("secondaryResult");
var oilValue = 0;
var primaryUnit = "";
var secondaryText = "";
if (fuelUnit === "gallons") {
// US Gallons to Fluid Ounces (128 oz per gallon)
oilValue = (fuelAmount * 128) / ratioValue;
primaryUnit = " fl oz (US Ounces)";
// Also provide ML for precision
var mlValue = (fuelAmount * 3785.41) / ratioValue;
secondaryText = "Equivalent to " + mlValue.toFixed(1) + " ml (Milliliters)";
} else if (fuelUnit === "liters") {
// Liters to Milliliters (1000 ml per liter)
oilValue = (fuelAmount * 1000) / ratioValue;
primaryUnit = " ml (Milliliters)";
// Also provide Ounces
var ozValue = (fuelAmount * 33.814) / ratioValue;
secondaryText = "Equivalent to " + ozValue.toFixed(2) + " fl oz";
} else if (fuelUnit === "gallons_uk") {
// Imperial Gallons to Imperial Ounces (160 oz per gallon)
oilValue = (fuelAmount * 160) / ratioValue;
primaryUnit = " fl oz (UK Imperial Ounces)";
var mlValueUK = (fuelAmount * 4546.09) / ratioValue;
secondaryText = "Equivalent to " + mlValueUK.toFixed(1) + " ml (Milliliters)";
}
primaryRes.innerHTML = oilValue.toFixed(2) + primaryUnit;
secondaryRes.innerHTML = secondaryText;
resultDisplay.style.display = "block";
}