Petrol Weight Calculator | Convert Fuel Volume to Mass (Kg & Lbs)
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Total Petrol Weight
37.25 kg
Formula Used: Weight = Volume (L) × (Base Density – (Temp – 15) × 0.00095)
Weight vs. Temperature Analysis
How the weight of this specific volume changes as temperature rises.
Volume to Weight Reference Table
| Volume |
Weight (kg) |
Weight (lbs) |
Calculated using current density settings.
What is a Petrol Weight Calculator?
A petrol weight calculator is a specialized tool designed to convert the volume of gasoline (measured in liters or gallons) into its mass (measured in kilograms or pounds). Unlike water, which has a relatively consistent density of 1 kg per liter, petrol is significantly lighter and its density fluctuates measurably with temperature changes.
This tool is essential for industries such as aviation, motorsports, and logistics, where fuel is often measured by volume at the pump but must be accounted for by weight for performance and safety calculations. Understanding the exact weight of your fuel load ensures accurate weight distribution, legal compliance in transportation, and precise fuel efficiency planning.
Petrol Weight Calculator Formula and Mathematical Explanation
The core physics behind the petrol weight calculator relies on the relationship between mass, volume, and density. The fundamental formula is:
Mass (m) = Volume (V) × Density (ρ)
However, petrol expands when heated and contracts when cooled. Therefore, the calculator must first adjust the density based on the current temperature relative to the standard reference temperature (usually 15°C). The adjusted formula used is:
1. Calculate Adjusted Density:
ρtemp = ρ15 – [(Tcurrent – 15) × Coefficient of Expansion]
2. Calculate Mass:
Weight = Volume (in Liters) × ρtemp
Variables Table
| Variable |
Meaning |
Unit |
Typical Range |
| V |
Volume of Fuel |
Liters (L) |
Any |
| ρ15 |
Base Density at 15°C |
kg/L |
0.710 – 0.775 |
| T |
Temperature |
Celsius (°C) |
-20°C to 50°C |
| CoE |
Coefficient of Expansion |
per °C |
~0.00095 |
Practical Examples (Real-World Use Cases)
Example 1: Formula 1 Racing Car
In motorsports, every kilogram matters. A race engineer needs to fuel a car with exactly 100 liters of premium unleaded petrol. The track temperature is hot, sitting at 30°C.
- Input Volume: 100 Liters
- Base Density: 0.755 kg/L (Premium)
- Temperature: 30°C (15 degrees above standard)
- Calculation: The density drops due to heat.
Adjustment: 0.755 – (15 × 0.00095) ≈ 0.7407 kg/L.
- Result: The fuel weighs approximately 74.07 kg. If they ignored temperature, they might have estimated 75.5 kg, an error of nearly 1.5 kg.
Example 2: Light Aircraft Refueling
A pilot is calculating the weight and balance for a Cessna 172. The tanks hold 50 US Gallons of Avgas (similar density to petrol). It is a cold morning at 5°C.
- Input Volume: 50 US Gallons (approx 189.27 Liters)
- Base Density: 0.720 kg/L (Avgas/Light Petrol)
- Temperature: 5°C (10 degrees below standard)
- Calculation: Cold fuel is denser.
Adjustment: 0.720 + (10 × 0.00095) ≈ 0.7295 kg/L.
- Result: 189.27 L × 0.7295 kg/L = 138.07 kg (approx 304 lbs).
How to Use This Petrol Weight Calculator
- Enter Volume: Input the total amount of fuel in the "Fuel Volume" field.
- Select Unit: Choose whether you are measuring in Liters, US Gallons, or Imperial Gallons.
- Set Temperature: Input the current temperature of the fuel. Remember, hotter fuel is lighter per liter.
- Choose Grade: Select the type of petrol (Standard, Premium, or Racing). Different grades have slightly different chemical compositions and densities.
- Review Results: Instantly see the weight in both Kilograms and Pounds in the results section.
Key Factors That Affect Petrol Weight Results
Several variables influence the final weight of your petrol load. Understanding these helps in making precise calculations using the petrol weight calculator.
- Temperature (Thermal Expansion): This is the most critical variable. Petrol has a high coefficient of thermal expansion. As it gets hotter, it expands in volume but its mass remains the same, meaning its density (weight per liter) decreases.
- Fuel Grade (Octane Rating): Premium fuels often contain different additives and aromatics compared to standard unleaded, leading to slight variations in specific gravity (density).
- Ethanol Content: Modern petrol often contains Ethanol (E10, E85). Ethanol is denser than pure gasoline (approx 0.789 kg/L vs 0.740 kg/L). Higher ethanol content generally increases the weight per liter.
- Atmospheric Pressure: While less significant than temperature for liquids, extreme changes in pressure can have minor effects on fluid density, though usually negligible for standard calculations.
- Measurement Accuracy: Pumps measure volume, not mass. If a pump is calibrated at 15°C but dispenses fuel at 25°C, you are technically getting less energy (mass) per liter than standard.
- Batch Variation: Refinery processes vary. Two batches of "Standard Unleaded" from different refineries can vary in density by up to 2-3%.
Frequently Asked Questions (FAQ)
Does petrol weigh the same as water?
No. Petrol is significantly lighter than water. While 1 liter of water weighs 1 kg, 1 liter of petrol typically weighs between 0.71 kg and 0.77 kg. It floats on top of water.
Why does temperature matter for petrol weight?
Liquids expand when heated. If you have a full tank of 50 liters at 10°C and it heats up to 30°C, the fuel will expand and may overflow, but the total weight remains the same. Conversely, a specific volume (e.g., 1 liter) weighs less at higher temperatures.
What is the standard density of petrol?
The industry standard reference density for petrol is typically around 0.745 kg/L at 15°C, though this varies by country and season (winter vs summer blends).
How do I convert US Gallons of gas to pounds?
One US Gallon of gasoline weighs approximately 6.0 to 6.3 pounds, depending on temperature and grade. Our calculator handles this conversion automatically.
Is diesel heavier than petrol?
Yes, diesel is denser and heavier. Diesel typically weighs around 0.832 kg/L to 0.850 kg/L, making it roughly 10-15% heavier than petrol by volume.
Does the octane rating affect weight?
Slightly. Higher octane fuels often contain denser aromatic hydrocarbons, making them marginally heavier than lower octane fuels, but the difference is usually small (0.01-0.02 kg/L).
Can I use this for aviation fuel calculations?
Yes, provided you select the correct density. Avgas (100LL) has a density similar to automotive petrol (approx 0.72 kg/L), but Jet A-1 is closer to diesel/kerosene (approx 0.80 kg/L).
What is the coefficient of expansion for petrol?
The commonly accepted average coefficient of thermal expansion for gasoline is 0.00095 per degree Celsius (or 0.00053 per degree Fahrenheit).
Related Tools and Resources
// Global Variables
var chartInstance = null;
// Constants
var US_GAL_TO_LITER = 3.78541;
var IMP_GAL_TO_LITER = 4.54609;
var KG_TO_LBS = 2.20462;
var EXPANSION_COEFFICIENT = 0.00095; // Per degree Celsius
var BASE_TEMP = 15; // Standard reference temp
// Initialization
window.onload = function() {
calculatePetrolWeight();
};
function calculatePetrolWeight() {
// 1. Get Inputs
var volumeInput = document.getElementById('volume');
var volumeVal = parseFloat(volumeInput.value);
var unit = document.getElementById('unit').value;
var temp = parseFloat(document.getElementById('temperature').value);
var densityType = document.getElementById('densityType');
var densityVal = parseFloat(densityType.value);
// Handle Custom Density Visibility
var customGroup = document.getElementById('customDensityGroup');
if (densityType.value === 'custom') {
customGroup.style.display = 'block';
densityVal = parseFloat(document.getElementById('customDensity').value);
} else {
customGroup.style.display = 'none';
}
// 2. Validation
var errorDiv = document.getElementById('volumeError');
if (isNaN(volumeVal) || volumeVal < 0) {
errorDiv.style.display = 'block';
return; // Stop calculation
} else {
errorDiv.style.display = 'none';
}
if (isNaN(temp)) temp = 15;
if (isNaN(densityVal)) densityVal = 0.745;
// 3. Convert Volume to Liters
var liters = 0;
if (unit === 'liters') {
liters = volumeVal;
} else if (unit === 'us_gallons') {
liters = volumeVal * US_GAL_TO_LITER;
} else if (unit === 'imp_gallons') {
liters = volumeVal * IMP_GAL_TO_LITER;
}
// 4. Calculate Density at Temperature
// Formula: D_new = D_base – (D_base * beta * deltaT) ??
// Simplified linear approximation often used in fuel logistics:
// Density changes by approx 0.00095 kg/L per degree C.
// D_temp = D_15 – ((Temp – 15) * 0.00095)
var tempDiff = temp – BASE_TEMP;
var adjustedDensity = densityVal – (tempDiff * EXPANSION_COEFFICIENT);
// Prevent unrealistic density (e.g. if temp is 500 degrees)
if (adjustedDensity < 0.5) adjustedDensity = 0.5;
// 5. Calculate Weight
var weightKg = liters * adjustedDensity;
var weightLbs = weightKg * KG_TO_LBS;
// 6. Update UI
document.getElementById('resultWeightKg').innerText = formatNumber(weightKg);
document.getElementById('resultWeightLbs').innerText = formatNumber(weightLbs) + " lbs";
document.getElementById('resultDensity').innerText = adjustedDensity.toFixed(4) + " kg/L";
document.getElementById('resultLiters').innerText = formatNumber(liters) + " L";
// 7. Update Visuals
updateTable(liters, adjustedDensity);
drawChart(liters, densityVal);
}
function formatNumber(num) {
return num.toLocaleString('en-US', { minimumFractionDigits: 2, maximumFractionDigits: 2 });
}
function resetCalculator() {
document.getElementById('volume').value = 50;
document.getElementById('unit').value = 'liters';
document.getElementById('temperature').value = 15;
document.getElementById('densityType').value = '0.745';
document.getElementById('customDensity').value = 0.745;
calculatePetrolWeight();
}
function copyResults() {
var weightKg = document.getElementById('resultWeightKg').innerText;
var weightLbs = document.getElementById('resultWeightLbs').innerText;
var density = document.getElementById('resultDensity').innerText;
var text = "Petrol Weight Calculation:\n" +
"Weight: " + weightKg + " kg (" + weightLbs + ")\n" +
"Adjusted Density: " + density + "\n" +
"Calculated via Petrol Weight Calculator.";
var tempInput = document.createElement("textarea");
tempInput.value = text;
document.body.appendChild(tempInput);
tempInput.select();
document.execCommand("copy");
document.body.removeChild(tempInput);
var btn = document.querySelector('.btn-copy');
var originalText = btn.innerText;
btn.innerText = "Copied!";
setTimeout(function(){ btn.innerText = originalText; }, 2000);
}
function updateTable(currentLiters, currentDensity) {
var tbody = document.querySelector('#referenceTable tbody');
tbody.innerHTML = "";
// Generate rows for 50%, 100%, 150%, 200% of input volume
var multipliers = [0.5, 1, 1.5, 2, 5, 10];
for (var i = 0; i < multipliers.length; i++) {
var m = multipliers[i];
var vol = currentLiters * m;
var wKg = vol * currentDensity;
var wLbs = wKg * KG_TO_LBS;
var row = "
" +
"| " + formatNumber(vol) + " L | " +
"" + formatNumber(wKg) + " | " +
"" + formatNumber(wLbs) + " | " +
"
";
tbody.innerHTML += row;
}
}
function drawChart(liters, baseDensity) {
var canvas = document.getElementById('petrolChart');
var ctx = canvas.getContext('2d');
// Clear canvas
ctx.clearRect(0, 0, canvas.width, canvas.height);
// Set dimensions
canvas.width = canvas.parentElement.offsetWidth;
canvas.height = 300;
var width = canvas.width;
var height = canvas.height;
var padding = 50;
// Data Generation: Weight vs Temperature (-10 to 40 degrees)
var temps = [-10, 0, 10, 15, 20, 30, 40];
var weights = [];
var minWeight = 999999;
var maxWeight = 0;
for (var i = 0; i < temps.length; i++) {
var t = temps[i];
var diff = t – BASE_TEMP;
var d = baseDensity – (diff * EXPANSION_COEFFICIENT);
var w = liters * d;
weights.push(w);
if (w maxWeight) maxWeight = w;
}
// Scaling
// Y Axis range: minWeight – padding to maxWeight + padding
var yMin = minWeight * 0.98;
var yMax = maxWeight * 1.02;
var yRange = yMax – yMin;
// Draw Axes
ctx.beginPath();
ctx.strokeStyle = '#ccc';
ctx.lineWidth = 1;
// Y Axis
ctx.moveTo(padding, 10);
ctx.lineTo(padding, height – padding);
// X Axis
ctx.lineTo(width – 10, height – padding);
ctx.stroke();
// Draw Line
ctx.beginPath();
ctx.strokeStyle = '#004a99';
ctx.lineWidth = 3;
var points = [];
for (var i = 0; i < temps.length; i++) {
var x = padding + ((i / (temps.length – 1)) * (width – padding – 20));
var y = height – padding – ((weights[i] – yMin) / yRange) * (height – padding – 20);
points.push({x: x, y: y, val: weights[i], temp: temps[i]});
if (i === 0) ctx.moveTo(x, y);
else ctx.lineTo(x, y);
}
ctx.stroke();
// Draw Points & Labels
ctx.fillStyle = '#004a99';
ctx.font = '12px Arial';
ctx.textAlign = 'center';
for (var i = 0; i < points.length; i++) {
var p = points[i];
// Dot
ctx.beginPath();
ctx.arc(p.x, p.y, 4, 0, Math.PI * 2);
ctx.fill();
// X Label (Temp)
ctx.fillStyle = '#666';
ctx.fillText(p.temp + "°C", p.x, height – padding + 20);
// Y Label (Weight) – only show first, middle, last to avoid clutter
if (i === 0 || i === 3 || i === 6) {
ctx.fillStyle = '#004a99';
ctx.fillText(p.val.toFixed(1) + "kg", p.x, p.y – 10);
}
}
// Axis Titles
ctx.save();
ctx.translate(15, height / 2);
ctx.rotate(-Math.PI / 2);
ctx.textAlign = "center";
ctx.fillStyle = "#333";
ctx.fillText("Weight (kg)", 0, 0);
ctx.restore();
ctx.fillText("Temperature (°C)", width / 2, height – 10);
}
// Handle resize for chart
window.onresize = function() {
calculatePetrolWeight();
};