Standard sidewalk is 4 inches. Driveways often 5-6 inches.
Materials Needed:
Total Volume:0.00 Cubic Yards
(Cubic Feet)0.00 ft³
Premix Bags Required:
📦
0 x 80lb Bags
📦
0 x 60lb Bags
*Includes estimated 5% waste safety margin.
function calculateConcrete() {
// Get input values
var length = document.getElementById('slabLength').value;
var width = document.getElementById('slabWidth').value;
var thick = document.getElementById('slabThickness').value;
var resultBox = document.getElementById('calcResult');
// Validation
if (!length || !width || !thick || length <= 0 || width <= 0 || thick <= 0) {
alert("Please enter valid positive numbers for all fields.");
resultBox.style.display = "none";
return;
}
// Convert strings to floats
var l = parseFloat(length);
var w = parseFloat(width);
var t = parseFloat(thick);
// Logic: Calculate Volume in Cubic Feet
// Thickness is in inches, so divide by 12 to get feet
var thicknessInFeet = t / 12;
var cubicFeet = l * w * thicknessInFeet;
// Logic: Convert to Cubic Yards (1 yard = 27 cubic feet)
var cubicYards = cubicFeet / 27;
// Add 5% safety margin for spillage/waste
var margin = 1.05;
var totalCubicFeet = cubicFeet * margin;
var totalCubicYards = cubicYards * margin;
// Logic: Calculate Bags
// Standard Yields:
// 80lb bag approx 0.60 cubic feet
// 60lb bag approx 0.45 cubic feet
var bags80 = Math.ceil(totalCubicFeet / 0.60);
var bags60 = Math.ceil(totalCubicFeet / 0.45);
// Update UI
document.getElementById('resYards').innerHTML = totalCubicYards.toFixed(2) + " Cubic Yards";
document.getElementById('resFeet').innerHTML = totalCubicFeet.toFixed(2) + " ft³";
document.getElementById('resBags80').innerHTML = bags80;
document.getElementById('resBags60').innerHTML = bags60;
// Show results
resultBox.style.display = "block";
}
How to Calculate Concrete for Your Project
Whether you are pouring a new patio, a driveway, or a simple shed base, calculating the correct amount of concrete is crucial. Ordering too little results in expensive second deliveries and cold joints, while ordering too much is a waste of money. Our Concrete Slab Calculator helps you determine exactly how much premix or ready-mix you need.
The Concrete Calculation Formula
To calculate concrete volume, you must determine the cubic footage of the area to be filled. The formula is:
Since concrete is typically sold by the Cubic Yard, you must divide the total cubic feet by 27.
Standard Slab Thickness Guide
4 Inches: Standard for sidewalks, patios, and residential shed bases.
5 Inches: Recommended for driveways that accommodate standard passenger vehicles.
6 Inches: Heavy-duty use, such as RV parking pads or heavy equipment floors.
How Many Bags of Concrete Do I Need?
If you are using pre-mixed bags (like Quikrete or Sakrete) for smaller projects, you need to know the yield of each bag:
80lb Bag: Yields approximately 0.60 cubic feet.
60lb Bag: Yields approximately 0.45 cubic feet.
Pro Tip: Always add a 5-10% safety margin to your calculation to account for uneven subgrades, spillage, and settling. Our calculator automatically includes a 5% buffer in the bag counts.