#concrete-calculator-wrapper .calc-box {
background-color: #f9f9f9;
padding: 25px;
border-radius: 8px;
box-shadow: 0 2px 5px rgba(0,0,0,0.05);
margin-bottom: 30px;
}
#concrete-calculator-wrapper h2 {
color: #333;
margin-top: 0;
border-bottom: 2px solid #0073aa;
padding-bottom: 10px;
margin-bottom: 20px;
}
#concrete-calculator-wrapper .form-row {
display: flex;
flex-wrap: wrap;
margin-bottom: 15px;
gap: 15px;
}
#concrete-calculator-wrapper .form-group {
flex: 1;
min-width: 140px;
}
#concrete-calculator-wrapper label {
display: block;
font-weight: bold;
margin-bottom: 5px;
color: #444;
font-size: 14px;
}
#concrete-calculator-wrapper input,
#concrete-calculator-wrapper select {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
#concrete-calculator-wrapper .btn-calc {
background-color: #0073aa;
color: white;
border: none;
padding: 15px 30px;
font-size: 18px;
font-weight: bold;
border-radius: 5px;
cursor: pointer;
width: 100%;
transition: background 0.3s;
margin-top: 10px;
}
#concrete-calculator-wrapper .btn-calc:hover {
background-color: #005177;
}
#concrete-calculator-wrapper .results-box {
margin-top: 25px;
padding: 20px;
background-color: #eef7fc;
border: 1px solid #cce5ff;
border-radius: 5px;
display: none;
}
#concrete-calculator-wrapper .result-item {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
padding-bottom: 10px;
border-bottom: 1px solid #ddd;
}
#concrete-calculator-wrapper .result-item:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
#concrete-calculator-wrapper .result-label {
color: #555;
font-size: 16px;
}
#concrete-calculator-wrapper .result-value {
font-weight: bold;
color: #000;
font-size: 18px;
}
#concrete-calculator-wrapper .article-content h3 {
color: #0073aa;
margin-top: 25px;
}
#concrete-calculator-wrapper .article-content p {
line-height: 1.6;
color: #333;
font-size: 16px;
}
#concrete-calculator-wrapper .article-content ul {
margin-bottom: 20px;
}
#concrete-calculator-wrapper .article-content li {
margin-bottom: 8px;
line-height: 1.5;
}
function calculateConcrete() {
// Get input values
var lFeet = parseFloat(document.getElementById("lengthFeet").value) || 0;
var lInch = parseFloat(document.getElementById("lengthInches").value) || 0;
var wFeet = parseFloat(document.getElementById("widthFeet").value) || 0;
var wInch = parseFloat(document.getElementById("widthInches").value) || 0;
var thick = parseFloat(document.getElementById("thickness").value) || 0;
var waste = parseFloat(document.getElementById("wasteFactor").value) || 1.0;
var price = parseFloat(document.getElementById("pricePerYard").value) || 0;
// Validate essential inputs
if (thick 0) {
totalCost = totalCubicYards * price;
}
// Display Results
document.getElementById("resYards").innerText = totalCubicYards.toFixed(2) + " yd³";
document.getElementById("resFeet").innerText = totalCubicFeet.toFixed(2) + " ft³";
document.getElementById("resBags80″).innerText = bags80 + " bags";
document.getElementById("resBags60″).innerText = bags60 + " bags";
var costRow = document.getElementById("costRow");
if (price > 0) {
costRow.style.display = "flex";
document.getElementById("resCost").innerText = "$" + totalCost.toFixed(2);
} else {
costRow.style.display = "none";
}
// Show results container
document.getElementById("results").style.display = "block";
}
Complete Guide to Calculating Concrete for Slabs
Whether you are pouring a patio, a driveway, or a shed foundation, calculating the correct amount of concrete is the most critical step in the planning process. Ordering too little can lead to disastrous "cold joints" where fresh concrete meets hardened concrete, creating weak points. Ordering too much wastes money and creates disposal issues.
Understanding the Concrete Formula
The basic formula for concrete volume is Length × Width × Thickness. However, because concrete is sold by the Cubic Yard (often just called a "yard") in the US, but dimensions are measured in feet and inches, conversion is necessary.
- Step 1: Convert all dimensions to feet. (e.g., 4 inches = 0.33 feet).
- Step 2: Multiply Length × Width × Thickness to get Cubic Feet.
- Step 3: Divide Cubic Feet by 27 to get Cubic Yards.
Why You Need a Safety Margin
Professional contractors never order the exact mathematical amount. Several factors contribute to volume loss during a pour:
- Spillage: Some concrete is always lost during transit from the truck/mixer to the form.
- Uneven Sub-grade: If your dirt base is just 1/2 inch lower in some spots, it can significantly increase the volume needed over a large area.
- Form Deflection: Wooden forms may bow slightly outward under the weight of the wet concrete.
We recommend a 5% safety margin for standard projects and up to 10% if excavating on uneven ground.
Thickness Guidelines
Choosing the right thickness affects both the cost and durability of your slab:
- 4 Inches: Standard for sidewalks, patios, and residential shed floors.
- 5-6 Inches: Recommended for driveways and areas holding heavier vehicles like RVs.
Pre-Mix Bags vs. Ready-Mix Truck
If your project requires less than 1 cubic yard of concrete (approx 45 bags of 80lb mix), mixing by hand or with a small rental mixer is usually cost-effective. For projects requiring over 1-2 yards, ordering a Ready-Mix truck is often cheaper and ensures a more consistent mix quality.