.concrete-calc-wrapper {
max-width: 600px;
margin: 20px auto;
padding: 25px;
background-color: #f8f9fa;
border: 1px solid #e0e0e0;
border-radius: 8px;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.concrete-calc-wrapper h2 {
text-align: center;
color: #333;
margin-top: 0;
margin-bottom: 20px;
}
.calc-input-group {
margin-bottom: 15px;
}
.calc-input-group label {
display: block;
margin-bottom: 5px;
font-weight: 600;
color: #555;
}
.calc-input-group input {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box; /* Ensures padding doesn't affect width */
font-size: 16px;
}
.calc-btn {
width: 100%;
padding: 12px;
background-color: #0073aa;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
margin-top: 10px;
transition: background-color 0.3s;
}
.calc-btn:hover {
background-color: #005177;
}
.calc-results {
margin-top: 25px;
padding: 20px;
background-color: #fff;
border: 1px solid #ddd;
border-radius: 4px;
display: none; /* Hidden by default */
}
.result-row {
display: flex;
justify-content: space-between;
padding: 8px 0;
border-bottom: 1px solid #eee;
}
.result-row:last-child {
border-bottom: none;
}
.result-label {
color: #666;
}
.result-value {
font-weight: bold;
color: #333;
}
.highlight-result {
color: #0073aa;
font-size: 1.1em;
}
.seo-content {
max-width: 800px;
margin: 40px auto;
font-family: sans-serif;
line-height: 1.6;
color: #333;
}
.seo-content h2, .seo-content h3 {
color: #2c3e50;
}
.tip-box {
background-color: #e8f4f8;
padding: 15px;
border-left: 4px solid #0073aa;
margin: 20px 0;
}
function calculateConcrete() {
// Get inputs
var length = parseFloat(document.getElementById('slabLength').value);
var width = parseFloat(document.getElementById('slabWidth').value);
var thickness = parseFloat(document.getElementById('slabThickness').value);
var resultsArea = document.getElementById('resultsArea');
// Validation
if (isNaN(length) || isNaN(width) || isNaN(thickness) || length <= 0 || width <= 0 || thickness <= 0) {
alert("Please enter valid positive numbers for all fields.");
resultsArea.style.display = 'none';
return;
}
// Logic
// 1. Convert thickness from inches to feet
var thicknessFeet = thickness / 12;
// 2. Calculate Cubic Feet
var cubicFeet = length * width * thicknessFeet;
// 3. Calculate Cubic Yards (27 cubic feet in 1 cubic yard)
var cubicYards = cubicFeet / 27;
// 4. Calculate Bags
// Standard yields:
// 80lb bag ~= 0.60 cubic feet
// 60lb bag ~= 0.45 cubic feet
// Add 5% waste factor for bags to be safe
var wasteFactor = 1.05;
var bags80 = Math.ceil((cubicFeet / 0.60) * wasteFactor);
var bags60 = Math.ceil((cubicFeet / 0.45) * wasteFactor);
// Update DOM
document.getElementById('resYards').innerHTML = cubicYards.toFixed(2) + " yd³";
document.getElementById('resFeet').innerHTML = cubicFeet.toFixed(2) + " ft³";
document.getElementById('resBags80').innerHTML = bags80 + " bags";
document.getElementById('resBags60').innerHTML = bags60 + " bags";
// Show results
resultsArea.style.display = 'block';
}
How to Calculate Concrete for Slabs, Patios, and Driveways
Whether you are pouring a new patio, a driveway extension, or a simple shed base, calculating the correct amount of concrete is the most critical step in the planning process. Ordering too little results in expensive "short load" fees or cold joints, while ordering too much is a waste of money and difficult to dispose of.
Understanding the Concrete Formula
Concrete is measured by volume. In the United States, large projects ordered from a ready-mix truck are measured in Cubic Yards, while smaller DIY projects using pre-mix bags are calculated based on Cubic Feet.
The basic formula for a slab is:
Length (ft) × Width (ft) × Thickness (ft) = Cubic Feet
To convert Cubic Feet to Cubic Yards, you divide the total by 27.
Recommended Thickness for Concrete Projects
The thickness of your slab depends entirely on its intended use. Using the calculator above, input your specific thickness to get an accurate estimate. Here are standard industry guidelines:
- 4 Inches: Standard for residential sidewalks, patios, and garage floors (accommodating standard passenger vehicles).
- 5-6 Inches: Recommended for driveways holding heavier trucks, RVs, or hot tub pads.
- 6+ Inches: Heavy industrial use or commercial foundations.
Pro Tip: The "Safety Margin"
Our calculator automatically adds a slight buffer when calculating bags, but if you are ordering a truck, always order 10% extra. This accounts for spillage, uneven subgrades (ground that isn't perfectly flat), and form settling. It is much cheaper to dump a small amount of extra concrete than to pay for a second delivery truck for the last 0.5 yards.
Bagged Concrete vs. Ready-Mix Truck
When should you buy bags, and when should you call a truck?
Use Pre-Mix Bags (60lb or 80lb) when:
- You need less than 1 cubic yard of concrete.
- The project site is inaccessible to a large truck.
- You are working solo and need to pace yourself.
Order a Ready-Mix Truck when:
- You need more than 1 cubic yard (approx. 45-60 bags).
- You need a consistent mix for a large visible area (driveway).
- You want a specific strength (PSI) or additive (fiber mesh, accelerants).
How many bags are in a yard?
If you are trying to convert cubic yards to bags manually: One cubic yard of concrete requires approximately 45 bags of 80lb mix or 60 bags of 60lb mix. This makes mixing a full yard by hand a very labor-intensive task!
Use the Concrete Slab Calculator above to get your exact numbers before heading to the hardware store.