Hex Head (+15%)
Socket Head (+10%)
Flat Head (+5%)
No Head (Stud)
Calculation Results
Weight per Bolt: 0kg
Total Batch Weight: 0kg
function updateUnits() {
var system = document.getElementById("unitSystem").value;
var labelDiam = document.getElementById("labelDiam");
var labelLength = document.getElementById("labelLength");
var unitLabels = document.getElementsByClassName("unitLabel");
if (system === "metric") {
labelDiam.innerHTML = "Bolt Diameter (mm)";
labelLength.innerHTML = "Bolt Length (mm)";
for (var i = 0; i < unitLabels.length; i++) {
unitLabels[i].innerHTML = "kg";
}
} else {
labelDiam.innerHTML = "Bolt Diameter (inches)";
labelLength.innerHTML = "Bolt Length (inches)";
for (var i = 0; i < unitLabels.length; i++) {
unitLabels[i].innerHTML = "lbs";
}
}
}
function calculateBoltWeight() {
var system = document.getElementById("unitSystem").value;
var density = parseFloat(document.getElementById("material").value); // g/cm3
var diameter = parseFloat(document.getElementById("diameter").value);
var length = parseFloat(document.getElementById("length").value);
var headFactor = parseFloat(document.getElementById("headFactor").value);
var quantity = parseFloat(document.getElementById("quantity").value);
if (isNaN(diameter) || isNaN(length) || isNaN(quantity) || diameter <= 0 || length <= 0) {
alert("Please enter valid positive dimensions.");
return;
}
var singleWeight = 0;
var totalWeight = 0;
if (system === "metric") {
// Volume in cm3 = PI * (r_cm)^2 * L_cm
var radius_cm = (diameter / 10) / 2;
var length_cm = length / 10;
var volume_cm3 = Math.PI * Math.pow(radius_cm, 2) * length_cm;
var mass_grams = volume_cm3 * density * headFactor;
singleWeight = mass_grams / 1000; // to kg
} else {
// Imperial: density in lb/in3 approx = (g/cm3 * 0.036127)
var density_lb_in3 = density * 0.036127;
var radius_in = diameter / 2;
var volume_in3 = Math.PI * Math.pow(radius_in, 2) * length;
singleWeight = volume_in3 * density_lb_in3 * headFactor;
}
totalWeight = singleWeight * quantity;
document.getElementById("singleWeight").innerText = singleWeight.toFixed(4);
document.getElementById("totalWeight").innerText = totalWeight.toFixed(3);
document.getElementById("resultContainer").style.display = "block";
}
Understanding Bolt Weight Calculations
Calculating the weight of fasteners is crucial for shipping logistics, structural load balancing, and inventory management. Whether you are working with standard metric M-series bolts or Imperial hex bolts, our calculator provides an accurate estimate based on material density and geometry.
The Mathematical Formula
The weight of a bolt is calculated by finding the volume of the cylindrical shank and then multiplying it by the material's density, plus the weight of the bolt head. The core formula used is:
Carbon Steel: 7.85 g/cm³ (Standard for Grade 8.8, 10.9)
Stainless Steel: 8.00 g/cm³ (304 and 316 series)
Aluminum: 2.70 g/cm³ (Lightweight applications)
Brass: 8.50 g/cm³ (Corrosion resistance and aesthetics)
Why Weight Matters in Engineering
In aerospace or automotive engineering, every gram counts. Using a bolt weight calculator helps engineers determine the "unsprung mass" of a vehicle or the total payload capacity for heavy-duty steel structures. Additionally, when purchasing bolts in bulk (e.g., 10,000 units), knowing the total weight is essential for calculating freight costs and ensuring your storage racks can handle the load.
Frequently Asked Questions
Does this include the nut and washer?
No, this calculator estimates the weight of the bolt only. If you are using nuts and washers, you should add approximately 20-30% additional weight or calculate them separately.
How accurate is the head factor?
The head factor is an approximation. A standard Hex Head bolt typically adds 15% more volume than a simple cylinder of the same diameter and length. For precise aerospace applications, refer to the manufacturer's specific technical data sheet.
What is the difference between Metric and Imperial weight calculation?
Metric calculations use millimeters and result in kilograms, whereas Imperial uses inches and results in pounds (lbs). The density values are automatically converted behind the scenes to match your selected unit system.