.calc-input-group { margin-bottom: 15px; }
.calc-label { display: block; margin-bottom: 5px; font-weight: 600; color: #333; }
.calc-input { width: 100%; padding: 10px; border: 1px solid #ddd; border-radius: 4px; box-sizing: border-box; font-size: 16px; }
.calc-btn { width: 100%; padding: 12px; background-color: #0073aa; color: white; border: none; border-radius: 4px; cursor: pointer; font-size: 18px; font-weight: bold; transition: background 0.3s; }
.calc-btn:hover { background-color: #005177; }
.calc-results { margin-top: 20px; padding: 15px; background-color: #fff; border: 1px solid #e5e5e5; border-radius: 4px; display: none; }
.result-row { display: flex; justify-content: space-between; padding: 8px 0; border-bottom: 1px solid #eee; }
.result-row:last-child { border-bottom: none; }
.result-label { color: #555; }
.result-value { font-weight: bold; color: #0073aa; }
.calc-article { margin-top: 40px; line-height: 1.6; color: #333; }
.calc-article h2 { color: #2c3e50; border-bottom: 2px solid #eee; padding-bottom: 10px; margin-top: 30px; }
.calc-article p { margin-bottom: 15px; }
.calc-article ul { margin-bottom: 15px; padding-left: 20px; }
.calc-article li { margin-bottom: 8px; }
Estimated Materials
Total Volume (Cubic Yards):
–
Total Volume (Cubic Feet):
–
80lb Premix Bags Needed:
–
60lb Premix Bags Needed:
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function calculateConcrete() {
var len = parseFloat(document.getElementById('slabLength').value);
var wid = parseFloat(document.getElementById('slabWidth').value);
var thick = parseFloat(document.getElementById('slabThickness').value);
var waste = parseFloat(document.getElementById('wasteFactor').value);
if (isNaN(len) || isNaN(wid) || isNaN(thick)) {
alert("Please enter valid numbers for length, width, and thickness.");
return;
}
if (isNaN(waste)) { waste = 0; }
// Logic: Volume in Cubic Feet = L * W * (Thickness in Inches / 12)
var thicknessInFeet = thick / 12;
var cubicFeetRaw = len * wid * thicknessInFeet;
// Add Waste
var totalCubicFeet = cubicFeetRaw * (1 + (waste / 100));
// Convert to Cubic Yards (27 cubic feet = 1 cubic yard)
var cubicYards = totalCubicFeet / 27;
// Calculate Bags
// Standard yield: 80lb bag ~= 0.6 cubic feet, 60lb bag ~= 0.45 cubic feet
var bags80 = Math.ceil(totalCubicFeet / 0.6);
var bags60 = Math.ceil(totalCubicFeet / 0.45);
// Display Results
document.getElementById('resYards').innerText = cubicYards.toFixed(2) + " cu. yd.";
document.getElementById('resFeet').innerText = totalCubicFeet.toFixed(2) + " cu. ft.";
document.getElementById('resBags80').innerText = bags80 + " bags";
document.getElementById('resBags60').innerText = bags60 + " bags";
document.getElementById('concreteResults').style.display = 'block';
}
How to Calculate Concrete for Slabs and Footings
Whether you are pouring a patio, a driveway, or footings for a deck, accurately estimating the amount of concrete required is the first step to a successful project. Ordering too little can result in catastrophic "cold joints" or structural weaknesses, while ordering too much is a waste of money and labor.
The Concrete Volume Formula
Concrete is measured by volume, specifically in Cubic Yards. To find this number manually, use the following formula:
- Step 1: Convert the thickness of your slab from inches to feet (divide inches by 12).
- Step 2: Multiply Length (ft) × Width (ft) × Thickness (ft) to get Cubic Feet.
- Step 3: Divide the Cubic Feet by 27 to get Cubic Yards.
For example, a 10′ x 10′ patio that is 4 inches thick would be calculated as: 10 × 10 × 0.33 = 33 cubic feet. Dividing 33 by 27 gives you approximately 1.22 cubic yards.
Why Include a Waste Factor?
In the construction industry, it is standard practice to include a margin of error. Ground surfaces are rarely perfectly level, and subgrades may settle slightly during the pour. Additionally, spillage occurs during mixing and transport. Our calculator defaults to a 10% safety margin to ensure you don't run short during the job.
Premix Bags vs. Ready-Mix Truck
Should you mix it yourself or call a truck? As a general rule of thumb:
- Under 1 Cubic Yard: It is usually more cost-effective to use premix bags (60lb or 80lb) and a rental mixer.
- Over 1 Cubic Yard: Calling a ready-mix delivery service is often preferred to save physical labor and ensure a consistent cure.
If you are using bags, remember that an 80lb bag of standard concrete mix yields approximately 0.6 cubic feet, while a 60lb bag yields about 0.45 cubic feet.