#concrete-calculator-container .calc-box {
background: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
padding: 25px;
margin-bottom: 30px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
#concrete-calculator-container h2 {
color: #2c3e50;
margin-top: 0;
margin-bottom: 20px;
font-size: 24px;
border-bottom: 2px solid #3498db;
padding-bottom: 10px;
}
#concrete-calculator-container .input-group {
margin-bottom: 15px;
display: flex;
flex-wrap: wrap;
gap: 15px;
align-items: flex-end;
}
#concrete-calculator-container .input-wrapper {
flex: 1;
min-width: 140px;
}
#concrete-calculator-container label {
display: block;
margin-bottom: 5px;
font-weight: 600;
font-size: 14px;
color: #555;
}
#concrete-calculator-container input[type="number"] {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
#concrete-calculator-container .calc-btn {
background-color: #3498db;
color: white;
border: none;
padding: 12px 24px;
font-size: 16px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
width: 100%;
transition: background-color 0.2s;
margin-top: 10px;
}
#concrete-calculator-container .calc-btn:hover {
background-color: #2980b9;
}
#concrete-calculator-container #results-area {
background-color: #fff;
border: 1px solid #dcdcdc;
padding: 20px;
margin-top: 20px;
border-radius: 6px;
display: none;
}
#concrete-calculator-container .result-row {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
padding-bottom: 10px;
border-bottom: 1px solid #eee;
}
#concrete-calculator-container .result-row:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
#concrete-calculator-container .result-label {
font-weight: 600;
color: #555;
}
#concrete-calculator-container .result-value {
font-weight: 700;
color: #2c3e50;
font-size: 18px;
}
#concrete-calculator-container .highlight-result {
color: #27ae60;
font-size: 22px;
}
#concrete-calculator-container .article-section h3 {
color: #2c3e50;
margin-top: 25px;
font-size: 20px;
}
#concrete-calculator-container .article-section ul {
padding-left: 20px;
}
#concrete-calculator-container .article-section li {
margin-bottom: 8px;
}
@media (max-width: 600px) {
#concrete-calculator-container .input-group {
flex-direction: column;
gap: 10px;
}
#concrete-calculator-container .input-wrapper {
width: 100%;
}
}
function calculateConcreteSlab() {
// Get inputs
var lenFt = parseFloat(document.getElementById('calc_length_ft').value) || 0;
var lenIn = parseFloat(document.getElementById('calc_length_in').value) || 0;
var widFt = parseFloat(document.getElementById('calc_width_ft').value) || 0;
var widIn = parseFloat(document.getElementById('calc_width_in').value) || 0;
var thickIn = parseFloat(document.getElementById('calc_thickness').value) || 0;
var quantity = parseFloat(document.getElementById('calc_quantity').value) || 1;
var price = parseFloat(document.getElementById('calc_price').value) || 0;
var waste = parseFloat(document.getElementById('calc_waste').value) || 0;
// Validation
if (thickIn <= 0 || quantity 0) {
document.getElementById('res_cost').textContent = totalCost.toFixed(2);
document.getElementById('cost-row').style.display = 'flex';
} else {
document.getElementById('cost-row').style.display = 'none';
}
document.getElementById('results-area').style.display = 'block';
}
How to Calculate Concrete for Your Project
Whether you are pouring a patio, a driveway, or footings for a deck, determining the correct amount of concrete is crucial for project success. Ordering too little can result in weak "cold joints" while waiting for a second delivery, while ordering too much wastes money and creates disposal issues. This Concrete Slab Calculator helps you estimate exactly how much ready-mix or pre-mix concrete you need.
Understanding the Concrete Formula
Concrete is measured by volume, specifically in Cubic Yards. The basic formula to calculate the concrete needed for a rectangular slab is:
(Length x Width x Thickness) / 27 = Cubic Yards
However, since measurements are often taken in feet and inches, the math requires several conversions:
- Convert the Thickness from inches to feet (Divide by 12).
- Multiply Length (ft) × Width (ft) × Thickness (ft) to get Cubic Feet.
- Divide the total Cubic Feet by 27 to get Cubic Yards.
The Importance of the "Waste Margin"
In the construction industry, it is standard practice to order slightly more concrete than the exact mathematical volume of your forms. This accounts for:
- Spillage during the pour.
- Uneven subgrade (dips in the ground) that increase slab depth in certain areas.
- Settling of the forms.
We recommend adding a 5% to 10% safety margin. Our calculator includes a customizable waste field (defaulted to 5%) to ensure you don't run short.
Pre-Mix Bags vs. Ready-Mix Truck
Should you buy bags from the hardware store or call a truck? It depends on the volume.
- Under 1 Cubic Yard: It is usually more economical to use pre-mix bags (60lb or 80lb).
- Over 1 Cubic Yard: Ordering a ready-mix truck is often cheaper and saves significant manual labor required for mixing.
Bag Yields:
- An 80lb bag of concrete yields approximately 0.60 cubic feet.
- A 60lb bag of concrete yields approximately 0.45 cubic feet.
Use the calculator above to see exactly how many bags your project requires compared to total cubic yards.
Example Calculation
Imagine you are pouring a patio that is 12 feet long, 10 feet wide, and 4 inches thick.
- Convert thickness: 4 inches ÷ 12 = 0.333 feet.
- Calculate volume: 12 x 10 x 0.333 = 40 cubic feet.
- Convert to yards: 40 ÷ 27 = 1.48 cubic yards.
- Add 5% waste: 1.48 x 1.05 = 1.55 cubic yards.
For this project, you would need approximately 1.55 cubic yards of concrete, or roughly 70 bags (80lb) if mixing by hand.