*Calculation based on standard asphalt density of approx. 145 lbs/ft³. Always add 5-10% for waste/compaction.
function calculateAsphalt() {
// Get inputs
var length = parseFloat(document.getElementById('asphaltLength').value);
var width = parseFloat(document.getElementById('asphaltWidth').value);
var depth = parseFloat(document.getElementById('asphaltDepth').value);
var price = parseFloat(document.getElementById('costPerTon').value);
// Validation
if (isNaN(length) || isNaN(width) || isNaN(depth) || length <= 0 || width <= 0 || depth 0) {
var totalCost = weightTons * price;
document.getElementById('costRow').style.display = 'flex';
document.getElementById('resCost').innerText = "$" + totalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
} else {
document.getElementById('costRow').style.display = 'none';
}
}
How to Calculate Tonnage for Asphalt
Calculating the correct amount of asphalt for a paving project is crucial for budgeting and ensuring structural integrity. Whether you are paving a residential driveway, a parking lot, or a roadway, the principle remains the same: you must determine the volume of the space and multiply it by the density of the asphalt mix.
The Asphalt Formula
The standard formula used by contractors and engineers involves three main dimensions: length, width, and thickness (depth). The result is converted from cubic volume into weight (tons).
The basic calculation steps are:
Calculate Area: Multiply Length (ft) × Width (ft) to get Square Footage.
Calculate Volume: Multiply the Area by the Thickness. Note: Since thickness is usually measured in inches, it must be divided by 12 to convert it to feet.
Determine Weight: Multiply the Volume (cubic feet) by the density of asphalt. The industry standard density is approximately 145 lbs per cubic foot (though this can vary between 140-150 lbs depending on the specific aggregate mix).
Convert to Tons: Divide the total weight in pounds by 2,000 to get the required tonnage.
The required thickness of your asphalt layer depends heavily on the intended use of the surface:
Residential Driveways (Resurfacing): 1.5 to 2 inches. Used when applying a new layer over existing asphalt in good condition.
New Residential Driveways: 3 to 4 inches. Typically laid in two lifts (layers) – a base coat and a surface coat – over a proper gravel base.
Commercial Parking Lots: 4 to 6 inches. Higher traffic areas require thicker pavement to withstand the weight of vehicles.
Heavy Duty / Industrial: 6 to 8+ inches. Necessary for loading docks or areas with heavy truck traffic.
Accounting for Waste and Compaction
It is important to note that hot mix asphalt compacts significantly when rolled. The "fluff factor" means that to achieve a compacted 2-inch depth, you may need to lay roughly 2.5 inches of loose material.
Furthermore, it is standard practice to order slightly more material than the exact mathematical calculation to account for:
Irregularities in the subgrade (low spots).
Waste during the spreading process.
Edges and transitions.
Most contractors recommend adding a 5% to 10% safety margin to your final tonnage calculation to ensure you do not run short in the middle of a pave.
Why Accurate Calculation Matters
Ordering too little asphalt ("shorting the job") is a paving nightmare. It creates cold joints where the first batch cools down before the second batch arrives, leading to weak seams and premature cracking. Conversely, ordering too much leads to wasted money on material that cannot be returned once it leaves the plant. Using a reliable asphalt calculator helps mitigate these risks.