Accurate freight classification is critical for LTL (Less Than Truckload) shipping. The freight class of your shipment determines the cost of transport. Carriers use the National Motor Freight Classification (NMFC) system to standardize pricing based on four main characteristics: density, stowability, handling, and liability. Of these, density is the most common factor used to determine class.
How is Freight Density Calculated?
Density is defined as the weight of the shipment (in pounds) divided by its volume (in cubic feet). The formula used by this calculator is:
The lower the density of your shipment, the higher the freight class (ranging from Class 50 to Class 400). Higher freight classes generally result in higher shipping rates because the cargo takes up more space relative to its weight.
Why This Calculation Matters
Providing an incorrect freight class on your Bill of Lading (BOL) can lead to costly "re-weighs" and "re-classifications" by the carrier. If a carrier inspects your freight and finds the density does not match the stated class, they will adjust the invoice to reflect the actual class, often adding administrative fees. Using a precision Freight Class Density Calculator ensures you quote and book your shipments accurately, protecting your profit margins.
function calculateFreightClass() {
var length = parseFloat(document.getElementById('fc-length').value);
var width = parseFloat(document.getElementById('fc-width').value);
var height = parseFloat(document.getElementById('fc-height').value);
var weight = parseFloat(document.getElementById('fc-weight').value);
var resultDiv = document.getElementById('fc-results');
if (isNaN(length) || isNaN(width) || isNaN(height) || isNaN(weight) || length <= 0 || width <= 0 || height <= 0 || weight <= 0) {
alert("Please enter valid positive numbers for all dimensions and weight.");
resultDiv.style.display = 'none';
return;
}
// 1. Calculate Cubic Inches
var cubicInches = length * width * height;
// 2. Calculate Cubic Feet (1728 cubic inches in a cubic foot)
var cubicFeet = cubicInches / 1728;
// 3. Calculate Density (lbs per cubic foot)
var density = weight / cubicFeet;
// 4. Determine Freight Class based on standard NMFC density guidelines
var freightClass = "";
if (density = 1 && density = 2 && density = 3 && density = 4 && density = 5 && density = 6 && density = 8 && density = 10 && density = 12 && density = 15 && density = 22.5 && density = 30 && density < 35) {
freightClass = "55";
} else {
freightClass = "50";
}
// Display Results
document.getElementById('res-volume').innerText = cubicFeet.toFixed(2) + " ft³";
document.getElementById('res-density').innerText = density.toFixed(2) + " lbs/ft³";
document.getElementById('res-class').innerText = "Class " + freightClass;
resultDiv.style.display = 'block';
}