.calc-container-specific {
max-width: 800px;
margin: 0 auto;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
color: #333;
line-height: 1.6;
}
.calc-box {
background: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
padding: 25px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
margin-bottom: 30px;
}
.calc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 20px;
font-size: 24px;
font-weight: 700;
}
.calc-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
.calc-group {
margin-bottom: 15px;
}
.calc-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
font-size: 14px;
color: #555;
}
.calc-input {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.calc-input:focus {
border-color: #0073aa;
outline: none;
box-shadow: 0 0 0 2px rgba(0,115,170,0.2);
}
.calc-btn {
grid-column: 1 / -1;
background-color: #0073aa;
color: white;
border: none;
padding: 12px 20px;
font-size: 16px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
width: 100%;
transition: background 0.3s;
}
.calc-btn:hover {
background-color: #005177;
}
.calc-results {
margin-top: 25px;
padding: 20px;
background: #fff;
border: 1px solid #ddd;
border-radius: 4px;
display: none;
}
.res-row {
display: flex;
justify-content: space-between;
padding: 10px 0;
border-bottom: 1px solid #eee;
}
.res-row:last-child {
border-bottom: none;
}
.res-label {
font-weight: 500;
color: #666;
}
.res-value {
font-weight: 700;
color: #2c3e50;
font-size: 18px;
}
.highlight {
color: #d35400;
font-size: 20px;
}
.content-section h2 {
color: #2c3e50;
margin-top: 30px;
font-size: 22px;
border-bottom: 2px solid #0073aa;
padding-bottom: 10px;
display: inline-block;
}
.content-section h3 {
color: #444;
font-size: 18px;
margin-top: 20px;
}
.content-section ul {
padding-left: 20px;
}
.content-section li {
margin-bottom: 10px;
}
@media (max-width: 600px) {
.calc-grid {
grid-template-columns: 1fr;
}
}
function calculateConcrete() {
// 1. Get input values
var length = parseFloat(document.getElementById("slabLength").value);
var width = parseFloat(document.getElementById("slabWidth").value);
var thickness = parseFloat(document.getElementById("slabThickness").value);
var waste = parseFloat(document.getElementById("wasteFactor").value);
// 2. Validate inputs
if (isNaN(length) || isNaN(width) || isNaN(thickness) || length <= 0 || width <= 0 || thickness <= 0) {
alert("Please enter valid positive numbers for all dimensions.");
return;
}
if (isNaN(waste) || waste < 0) {
waste = 0;
}
// 3. Calculate Volume in Cubic Feet
// Convert thickness from inches to feet
var thicknessFeet = thickness / 12;
var volumeCuFt = length * width * thicknessFeet;
// 4. Apply Waste Factor
var wasteMultiplier = 1 + (waste / 100);
var totalCuFt = volumeCuFt * wasteMultiplier;
// 5. Calculate Cubic Yards
var totalCuYards = totalCuFt / 27;
// 6. Calculate Bags
// Typical yield: 80lb bag = 0.6 cu ft, 60lb bag = 0.45 cu ft
var bags80 = totalCuFt / 0.6;
var bags60 = totalCuFt / 0.45;
// 7. Display Results
// Round Yards and Feet to 2 decimal places
document.getElementById("resYards").innerHTML = totalCuYards.toFixed(2);
document.getElementById("resFeet").innerHTML = totalCuFt.toFixed(2);
// Round bags up to the nearest whole number (you can't buy half a bag)
document.getElementById("resBags80").innerHTML = Math.ceil(bags80);
document.getElementById("resBags60").innerHTML = Math.ceil(bags60);
// Show results area
document.getElementById("resultsArea").style.display = "block";
}
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"@type": "Question",
"name": "How do I calculate how much concrete I need?",
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"text": "Multiply length (ft) by width (ft) by thickness (ft) to get cubic feet. Divide by 27 to get cubic yards. Always add 5-10% for waste."
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"@type": "Question",
"name": "How many 80lb bags of concrete make a yard?",
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"text": "A standard concrete driveway should be at least 4 inches thick. For heavier vehicles, 5 to 6 inches is recommended."
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Concrete Slab Calculator
Cubic Yards Needed:
0.00
Cubic Feet Needed:
0.00
80lb Premix Bags:
0
60lb Premix Bags:
0
How to Calculate Concrete for a Slab
Calculating the correct amount of concrete is crucial for any construction project to avoid expensive shortages or wasteful overage. This Concrete Slab Calculator determines the exact volume required based on your dimensions and adds a safety margin for spillage and uneven subgrades.
The Concrete Formula
To calculate the volume of a concrete slab manually, you must convert all dimensions to feet and use the following formula:
Volume (Cubic Feet) = Length (ft) × Width (ft) × (Thickness (in) ÷ 12)
Since concrete is typically sold by the Cubic Yard (if ordering a truck) or by the bag (if mixing yourself), you need to convert cubic feet:
- Cubic Yards: Divide Cubic Feet by 27.
- 80lb Bags: Divide Cubic Feet by 0.60 (approximate yield).
- 60lb Bags: Divide Cubic Feet by 0.45 (approximate yield).
Standard Slab Thickness Guide
Choosing the right thickness depends on the intended use of the slab:
- 4 Inches: Standard for residential sidewalks, patios, and garage floors for passenger cars.
- 5-6 Inches: Recommended for driveways that hold heavier vehicles (trucks, RVs) or shed foundations.
- 8+ Inches: Heavy-duty commercial or industrial applications.
Premix Bags vs. Ready-Mix Truck
When should you order a truck versus buying bags? A general rule of thumb is the 1 Yard Rule.
If your project requires more than 1 cubic yard of concrete (approx. 45 bags of 80lb mix), it is often more cost-effective and physically manageable to order a ready-mix truck. For projects under 1 yard, such as small patio extensions or setting posts, buying bags is usually the better option.
Why Include a Waste Factor?
Professional contractors always include a waste margin, typically 5% to 10%. This accounts for:
- Spillage during the pour.
- Uneven ground (subgrade) that may be deeper in some spots.
- Concrete remaining inside the mixer or wheelbarrow.
Our calculator automatically applies your selected waste percentage to ensure you don't run short.