Gas Ratio Calculator

2-Stroke Fuel Mixture Calculator

US Gallons Liters

: 1

Common: 32, 40, or 50

Calculation Result

function calculateGasRatio() { var gasVol = parseFloat(document.getElementById("gasVolume").value); var unit = document.getElementById("volumeUnit").value; var ratio = parseFloat(document.getElementById("ratioPart").value); var resultDiv = document.getElementById("gasRatioResult"); var resultText = document.getElementById("resultText"); var altText = document.getElementById("alternateUnitText"); if (isNaN(gasVol) || gasVol <= 0 || isNaN(ratio) || ratio <= 0) { alert("Please enter valid numbers for gasoline volume and ratio."); return; } resultDiv.style.display = "block"; if (unit === "gallons") { // Calculate in fluid ounces (1 gallon = 128 fluid ounces) var totalOunces = gasVol * 128; var oilNeededOz = totalOunces / ratio; resultText.innerHTML = "Add " + oilNeededOz.toFixed(2) + " fl oz of oil"; // Provide ML conversion for convenience var oilNeededMl = oilNeededOz * 29.5735; altText.innerHTML = "Equivalent to: " + oilNeededMl.toFixed(0) + " ml"; } else { // Calculate in liters/milliliters (1 liter = 1000 ml) var totalMl = gasVol * 1000; var oilNeededMl = totalMl / ratio; resultText.innerHTML = "Add " + oilNeededMl.toFixed(1) + " ml of oil"; // Provide liters conversion var oilLiters = oilNeededMl / 1000; altText.innerHTML = "Equivalent to: " + oilLiters.toFixed(3) + " Liters"; } }

How to Use the Gas Ratio Calculator

Whether you are preparing fuel for a chainsaw, weed whacker, outboard motor, or a vintage dirt bike, getting the correct gas-to-oil mixture is critical for engine health. Too much oil leads to heavy smoke and carbon buildup; too little oil results in friction that can seize the engine permanently.

Understanding the Ratio (e.g., 50:1)

The numbers represent the parts of gasoline relative to the parts of oil. For example, 50:1 means that for every 50 units of gasoline, you must add 1 unit of 2-stroke oil. Our calculator handles the math for you, converting these ratios into manageable measurements like fluid ounces or milliliters.

Common Mixture Ratios

Ratio	Gasoline	Oil (US fl oz)	Oil (ml)
32:1	1 Gallon	4.0 oz	118 ml
40:1	1 Gallon	3.2 oz	95 ml
50:1	1 Gallon	2.6 oz	77 ml

Best Practices for Mixing 2-Stroke Fuel

• Use Fresh Fuel: Gasoline begins to degrade after 30 days. Use fresh 89+ octane fuel for best performance.
• The Order Matters: Always pour the oil into the gas can first, then add the gasoline. This helps the fuel and oil mix naturally as the gas flows in.
• Shake Well: Always give your fuel container a good shake before fueling your equipment, as oil can settle over time.
• Avoid "Pre-Mixed" Risks: Unless you are buying expensive engineered fuel, never guess the ratio. Use this calculator to ensure precision.

Example Calculation

If your manual calls for a 40:1 ratio and you have 2.5 gallons of gas:

1. Convert gallons to ounces: 2.5 x 128 = 320 oz.
2. Divide by the ratio: 320 / 40 = 8 oz.
3. Result: Add exactly 8 fluid ounces of 2-stroke oil to your gas can.