.calculator-widget {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 2rem auto;
border: 1px solid #e2e8f0;
border-radius: 8px;
overflow: hidden;
background: #ffffff;
box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
}
.calc-header {
background: #2b6cb0;
color: white;
padding: 1.5rem;
text-align: center;
}
.calc-header h2 {
margin: 0;
font-size: 1.5rem;
}
.calc-body {
padding: 2rem;
display: grid;
grid-template-columns: 1fr 1fr;
gap: 2rem;
}
@media (max-width: 768px) {
.calc-body {
grid-template-columns: 1fr;
}
}
.input-group {
margin-bottom: 1.5rem;
}
.input-group label {
display: block;
font-weight: 600;
margin-bottom: 0.5rem;
color: #2d3748;
}
.input-group input, .input-group select {
width: 100%;
padding: 0.75rem;
border: 1px solid #cbd5e0;
border-radius: 4px;
font-size: 1rem;
box-sizing: border-box;
}
.input-group input:focus {
outline: none;
border-color: #2b6cb0;
box-shadow: 0 0 0 3px rgba(43, 108, 176, 0.2);
}
.calc-actions {
grid-column: 1 / -1;
text-align: center;
margin-top: 1rem;
}
.calc-btn {
background: #ed8936;
color: white;
border: none;
padding: 1rem 2rem;
font-size: 1.1rem;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background 0.2s;
}
.calc-btn:hover {
background: #dd6b20;
}
.results-area {
grid-column: 1 / -1;
background: #f7fafc;
padding: 1.5rem;
border-radius: 6px;
margin-top: 1rem;
border: 1px solid #e2e8f0;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
padding: 0.75rem 0;
border-bottom: 1px solid #edf2f7;
}
.result-row:last-child {
border-bottom: none;
}
.result-label {
color: #4a5568;
font-weight: 500;
}
.result-value {
color: #2d3748;
font-weight: 700;
font-size: 1.1rem;
}
.highlight-result {
color: #2b6cb0;
font-size: 1.25rem;
}
.content-section {
max-width: 800px;
margin: 3rem auto;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
line-height: 1.6;
color: #2d3748;
}
.content-section h2 {
color: #2b6cb0;
border-bottom: 2px solid #e2e8f0;
padding-bottom: 0.5rem;
margin-top: 2rem;
}
.content-section h3 {
color: #2c5282;
margin-top: 1.5rem;
}
.content-section ul {
padding-left: 1.5rem;
}
.content-section li {
margin-bottom: 0.5rem;
}
.info-box {
background: #ebf8ff;
border-left: 4px solid #2b6cb0;
padding: 1rem;
margin: 1.5rem 0;
}
function calculateConcrete() {
// Retrieve inputs by ID
var length = document.getElementById('slabLength').value;
var width = document.getElementById('slabWidth').value;
var thick = document.getElementById('slabThickness').value;
var waste = document.getElementById('wasteFactor').value;
var resultBox = document.getElementById('resultContainer');
// Validation: Ensure inputs are numbers and not empty
if (length === "" || width === "" || thick === "" || isNaN(length) || isNaN(width) || isNaN(thick)) {
alert("Please enter valid numbers for Length, Width, and Thickness.");
resultBox.style.display = 'none';
return;
}
// Parse values to floats
var lenVal = parseFloat(length);
var widVal = parseFloat(width);
var thickVal = parseFloat(thick);
var wasteVal = parseFloat(waste);
if (lenVal <= 0 || widVal <= 0 || thickVal <= 0) {
alert("Values must be greater than zero.");
return;
}
// Logic: Calculate Cubic Feet
// Formula: Length (ft) * Width (ft) * (Thickness (in) / 12)
var thicknessInFeet = thickVal / 12;
var cubicFeet = lenVal * widVal * thicknessInFeet;
// Apply Waste Factor
var wasteMultiplier = 1 + (wasteVal / 100);
var totalCubicFeet = cubicFeet * wasteMultiplier;
// Logic: Calculate Cubic Yards
// 1 Cubic Yard = 27 Cubic Feet
var totalCubicYards = totalCubicFeet / 27;
// Logic: Calculate Bags
// Standard yield: 80lb bag ≈ 0.60 cubic feet, 60lb bag ≈ 0.45 cubic feet
var bags80 = Math.ceil(totalCubicFeet / 0.60);
var bags60 = Math.ceil(totalCubicFeet / 0.45);
// 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";
// Show the result container
resultBox.style.display = 'block';
}
How to Calculate Concrete for Your Project
Whether you are pouring a patio, a driveway, or footings for a deck, accurate calculation of concrete volume is essential to avoid running out of material mid-pour or overspending on waste. This Concrete Slab & Footing Calculator simplifies the math by converting your dimensions into Cubic Yards and standard pre-mix bag counts.
The Concrete Volume Formula
Concrete is sold by volume, typically in Cubic Yards (for truck deliveries) or Cubic Feet (for pre-mixed bags). The basic formula for a rectangular slab is:
Volume = Length (ft) × Width (ft) × Thickness (ft)
Since most people measure thickness in inches, you must first divide the inches by 12 to convert them to feet. For example, a 4-inch thick slab is 0.33 feet thick.
Calculating Cubic Yards
Once you have the total cubic feet, divide that number by 27. There are 27 cubic feet in one cubic yard. Ready-mix trucks usually require a minimum order (often 1 yard), so for small projects under 1 yard, bags are usually more economical.
How Many Bags Do I Need?
If you are using pre-mixed concrete bags from a hardware store, the yield depends on the bag weight:
- 80lb Bag: Yields approximately 0.60 cubic feet.
- 60lb Bag: Yields approximately 0.45 cubic feet.
Our calculator rounds up to the nearest whole bag to ensure you have enough material.
Why Include a Safety Margin?
It is industry standard to add a 5% to 10% safety margin (or waste factor) to your order. This accounts for:
- Uneven sub-grade or ground settling.
- Spillage during the pour.
- Variations in formwork dimensions.
For a perfectly flat, compacted base, 5% is sufficient. For excavation into uneven ground, consider using 10%.
Standard Thickness Guide
- 4 Inches: Standard for sidewalks, patios, and residential driveways (passenger cars).
- 5-6 Inches: Recommended for heavier driveways (trucks/SUVs) or hot tub pads.
- 8+ Inches: Heavy-duty foundations or commercial aprons.