.calculator-wrapper {
max-width: 800px;
margin: 0 auto;
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
color: #333;
line-height: 1.6;
}
.calc-container {
background: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.calc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 24px;
font-weight: 700;
}
.input-group {
margin-bottom: 20px;
}
.input-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #495057;
}
.input-group input {
width: 100%;
padding: 12px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box; /* Fixes padding width issue */
}
.input-group input:focus {
border-color: #f39c12;
outline: none;
box-shadow: 0 0 0 3px rgba(243, 156, 18, 0.25);
}
.input-row {
display: flex;
gap: 20px;
flex-wrap: wrap;
}
.input-col {
flex: 1;
min-width: 200px;
}
.calc-btn {
display: block;
width: 100%;
background-color: #f39c12;
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background-color 0.2s;
margin-top: 10px;
}
.calc-btn:hover {
background-color: #d68910;
}
.results-box {
background-color: #fff;
border: 1px solid #dee2e6;
border-radius: 4px;
padding: 20px;
margin-top: 30px;
display: none; /* Hidden by default */
}
.result-item {
display: flex;
justify-content: space-between;
align-items: center;
padding: 12px 0;
border-bottom: 1px solid #eee;
}
.result-item:last-child {
border-bottom: none;
}
.result-label {
font-weight: 600;
color: #555;
}
.result-value {
font-weight: 700;
color: #2c3e50;
font-size: 18px;
}
.article-content {
margin-top: 50px;
padding: 20px;
background: #fff;
}
.article-content h2 {
color: #2c3e50;
border-bottom: 2px solid #f39c12;
padding-bottom: 10px;
margin-top: 30px;
}
.article-content h3 {
color: #34495e;
margin-top: 25px;
}
.article-content p {
margin-bottom: 15px;
font-size: 16px;
}
.article-content ul {
margin-bottom: 15px;
padding-left: 20px;
}
.article-content li {
margin-bottom: 8px;
}
.note {
font-size: 0.9em;
color: #7f8c8d;
font-style: italic;
margin-top: 10px;
}
function calculateConcrete() {
// Get input values using var
var len = document.getElementById('slabLength').value;
var wid = document.getElementById('slabWidth').value;
var thick = document.getElementById('slabThickness').value;
var resultBox = document.getElementById('resultBox');
// Validate inputs
if (len === "" || wid === "" || thick === "" || len <= 0 || wid <= 0 || thick <= 0) {
alert("Please enter valid positive numbers for Length, Width, and Thickness.");
return;
}
// Convert inputs to numbers
var lengthFt = parseFloat(len);
var widthFt = parseFloat(wid);
var thicknessIn = parseFloat(thick);
// Logic: Calculate Volume
// 1. Convert thickness to feet
var thicknessFt = thicknessIn / 12;
// 2. Calculate Cubic Feet
var cubicFeet = lengthFt * widthFt * thicknessFt;
// 3. Add 10% Safety Margin for waste/spillage/uneven subgrade
var cubicFeetSafe = cubicFeet * 1.10;
// 4. Calculate Cubic Yards (1 Yard = 27 Cubic Feet)
var cubicYards = cubicFeetSafe / 27;
// 5. Calculate Bags
// Standard Yield:
// 80lb bag ~= 0.60 cubic feet
// 60lb bag ~= 0.45 cubic feet
var bags80 = Math.ceil(cubicFeetSafe / 0.60);
var bags60 = Math.ceil(cubicFeetSafe / 0.45);
// Display Results
document.getElementById('resYards').innerHTML = cubicYards.toFixed(2) + " yd³";
document.getElementById('resFeet').innerHTML = cubicFeetSafe.toFixed(2) + " ft³";
document.getElementById('res80bags').innerHTML = bags80 + " bags";
document.getElementById('res60bags').innerHTML = bags60 + " bags";
// Show result box
resultBox.style.display = "block";
}
How to Calculate Concrete for Your Project
Whether you are pouring a new patio, a driveway, or a simple shed foundation, knowing exactly how much concrete to order is crucial. Ordering too little can result in a disastrous "cold joint" in your slab, while ordering too much is a waste of money. This Concrete Slab Calculator helps you determine the precise volume required, including a standard safety margin.
Understanding the Formula
The math behind calculating concrete volume is relatively simple geometry, but unit conversion is where most mistakes happen. Concrete is typically sold by the Cubic Yard (if ordering a truck) or by the bag (if mixing yourself).
The basic formula is:
Length (ft) × Width (ft) × Thickness (ft) = Cubic Feet
Since slab thickness is usually measured in inches, you must divide the inches by 12 before multiplying. Finally, to get Cubic Yards, divide the total Cubic Feet by 27.
Standard Thickness Guidelines
Choosing the right thickness is vital for the longevity of your slab:
- 4 Inches: Standard for walkways, patios, and shed floors. Suitable for foot traffic and light loads.
- 5-6 Inches: Recommended for driveways considering standard passenger vehicles.
- 6+ Inches: Required for heavy-duty driveways (RVs, heavy trucks) or structural foundations.
Pre-Mixed Bags vs. Ready-Mix Truck
Once you have your calculation, you need to decide how to buy the concrete:
Bagged Concrete: Best for small jobs (under 1-2 cubic yards). Our calculator provides estimates for standard 80lb and 60lb bags found at home improvement stores. Note that an 80lb bag yields approximately 0.60 cubic feet of cured concrete.
Ready-Mix Truck: If your project requires more than 2 cubic yards (approx. 90-100 bags of 80lb mix), it is usually more economical and physically easier to order a ready-mix truck delivery. Trucks ensure a consistent mix and allow you to pour the entire slab at once.
Why the Safety Margin?
This calculator automatically adds a 10% safety margin to the total volume. This accounts for spillage during the pour, uneven subgrade (ground) depth, and the fact that wooden forms may bow slightly under the weight of wet concrete. It is always better to have a little extra concrete left over than to run out before the job is done.