body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
max-width: 1200px;
margin: 0 auto;
padding: 20px;
background-color: #f9f9f9;
}
.calc-container {
background: #ffffff;
border: 1px solid #e1e1e1;
border-radius: 8px;
padding: 30px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
margin-bottom: 40px;
max-width: 800px;
margin-left: auto;
margin-right: auto;
}
.calc-title {
text-align: center;
margin-bottom: 25px;
color: #2c3e50;
font-size: 24px;
font-weight: 700;
border-bottom: 2px solid #3498db;
padding-bottom: 10px;
}
.input-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
margin-bottom: 20px;
}
@media (max-width: 600px) {
.input-grid {
grid-template-columns: 1fr;
}
}
.form-group {
display: flex;
flex-direction: column;
}
.form-group label {
font-weight: 600;
margin-bottom: 8px;
color: #444;
}
.form-group input, .form-group select {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
}
.form-group input:focus {
border-color: #3498db;
outline: none;
}
.calc-btn {
width: 100%;
padding: 15px;
background-color: #3498db;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background-color 0.2s;
margin-top: 10px;
}
.calc-btn:hover {
background-color: #2980b9;
}
.results-area {
margin-top: 30px;
background-color: #f1f8ff;
border-radius: 6px;
padding: 20px;
border-left: 5px solid #3498db;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
padding: 10px 0;
border-bottom: 1px solid #dceefc;
}
.result-row:last-child {
border-bottom: none;
}
.result-label {
font-weight: 600;
color: #555;
}
.result-value {
font-weight: 700;
color: #2c3e50;
}
.article-section {
background: #fff;
padding: 40px;
border-radius: 8px;
border: 1px solid #e1e1e1;
}
h2 {
color: #2c3e50;
margin-top: 30px;
}
h3 {
color: #34495e;
margin-top: 25px;
}
p {
margin-bottom: 15px;
}
ul {
margin-bottom: 20px;
padding-left: 20px;
}
li {
margin-bottom: 8px;
}
.highlight-box {
background-color: #fff8e1;
border: 1px solid #ffe0b2;
padding: 15px;
border-radius: 4px;
margin: 20px 0;
}
function calculateConcrete() {
// Get input values
var length = document.getElementById('slabLength').value;
var width = document.getElementById('slabWidth').value;
var thick = document.getElementById('slabThickness').value;
var waste = document.getElementById('wastePct').value;
// Validation
if (length === "" || width === "" || thick === "") {
alert("Please enter values for Length, Width, and Thickness.");
return;
}
var lenVal = parseFloat(length);
var widVal = parseFloat(width);
var thkVal = parseFloat(thick);
var wasteVal = parseFloat(waste);
if (isNaN(lenVal) || isNaN(widVal) || isNaN(thkVal)) {
alert("Please enter valid numbers.");
return;
}
if (isNaN(wasteVal)) {
wasteVal = 0;
}
// Calculations
// 1. Calculate Cubic Feet (Length * Width * (Thickness/12))
var thicknessInFeet = thkVal / 12;
var rawCubicFeet = lenVal * widVal * thicknessInFeet;
// 2. Add Wastage
var wasteMultiplier = 1 + (wasteVal / 100);
var totalCubicFeet = rawCubicFeet * wasteMultiplier;
// 3. Convert to Cubic Yards (1 Yard = 27 Cubic Feet)
var totalCubicYards = totalCubicFeet / 27;
// 4. Calculate Bags
// Standard pre-mix yield is approx 0.60 cu ft per 80lb bag and 0.45 cu ft per 60lb bag
var yield80 = 0.60;
var yield60 = 0.45;
var bags80 = Math.ceil(totalCubicFeet / yield80);
var bags60 = Math.ceil(totalCubicFeet / yield60);
// 5. Calculate Weight (Average concrete is ~145-150 lbs per cubic foot)
// Using 145 lbs/ft^3 for cured concrete estimate
var totalWeight = totalCubicFeet * 145;
// Display Results
document.getElementById('resYards').innerHTML = totalCubicYards.toFixed(2) + " yd³";
document.getElementById('resFeet').innerHTML = totalCubicFeet.toFixed(2) + " ft³";
document.getElementById('resBags80').innerHTML = bags80 + " bags";
document.getElementById('resBags60').innerHTML = bags60 + " bags";
document.getElementById('resWeight').innerHTML = Math.round(totalWeight).toLocaleString() + " lbs";
// Show result div
document.getElementById('results').style.display = "block";
}
Guide to Calculating Concrete Slabs
Planning a patio, driveway, or shed foundation requires accurate calculation of concrete volume to ensure you order enough material without excessive waste. Concrete is typically measured in cubic yards, but pre-mixed bags (sold at hardware stores) are sold by weight. This calculator helps bridge that gap.
1. Measuring Your Project
To get an accurate estimate, measure the length and width of your formwork in feet. Ensure your corners are square. If your project is an irregular shape, divide it into smaller rectangles, calculate the volume for each, and add them together.
2. Determining the Right Thickness
The thickness of your slab depends heavily on its intended use. Here are industry standards:
- 4 Inches: Standard for residential sidewalks, patios, and shed bases.
- 5-6 Inches: Recommended for driveways accommodating passenger vehicles.
- 6-8 Inches: Required for heavy equipment or commercial aprons.
Pro Tip: Always account for measuring errors and uneven subgrades by adding a "Wastage" or "Safety Margin" percentage. A standard safety margin is 5% to 10%.
3. Bags vs. Ready-Mix Truck
When should you mix it yourself versus ordering a truck?
Use Bags (Pre-mix): For projects requiring less than 1 cubic yard (approx. 45-50 bags of 80lb concrete). This is ideal for setting fence posts, small pads, or repairs.
Order a Truck: For projects exceeding 1 cubic yard. Mixing more than 50 bags by hand is labor-intensive and makes it difficult to achieve a consistent finish before the concrete begins to cure.
4. Understanding the Math
The formula used in the calculator above is:
(Length × Width × Thickness in Feet) ÷ 27 = Cubic Yards
Since thickness is usually measured in inches, we first divide the inches by 12 to convert to feet before multiplying.