Concrete Slab Cost Calculator & Estimator
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.calculator-wrapper {
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.calc-inputs h3, .calc-results h3 {
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Estimated Material & Cost
Total Area:
0 sq ft
Total Volume:
0 cu yds
Material Cost:
$0.00
Estimated Labor:
$0.00
Total Estimate:
$0.00
DIY Premix Calculation:
For small jobs using premix bags:
• 80lb Bags needed: 0
• 60lb Bags needed: 0
Concrete Slab Cost Calculator & Guide
Planning a new patio, driveway, or shed foundation? Accurately estimating the amount of concrete needed is critical to avoiding mid-pour shortages or paying for excessive waste. Our Concrete Slab Cost Calculator helps you determine the exact cubic yards required and provides a financial estimate based on current market rates.
How to Calculate Concrete for a Slab
Concrete is typically measured in cubic yards (often just called "yards"). One cubic yard is equal to 27 cubic feet. To calculate the volume manually, use the following formula:
- Step 1: Multiply Length (ft) × Width (ft) to get Square Footage.
- Step 2: Convert the slab thickness from inches to feet (e.g., 4 inches ÷ 12 = 0.33 feet).
- Step 3: Multiply Square Footage × Thickness (in ft) to get Cubic Feet.
- Step 4: Divide Cubic Feet by 27 to get Cubic Yards.
Note: It is industry standard to add a safety margin (usually 5% to 10%) to account for spillage, uneven subgrades, and form spreading.
Recommended Thickness Guide
The thickness of your slab depends entirely on its intended use:
- 4 Inches: The standard for residential sidewalks, patios, and garage floors for passenger cars.
- 5 Inches: Recommended for heavier traffic or if the subgrade is less stable.
- 6 Inches: Required for driveways hosting heavy trucks, RVs, or heavy machinery.
Concrete Pricing Factors (2024 Estimates)
When budgeting for your project, consider these cost components:
- Ready-Mix Concrete: Prices typically range from $125 to $150 per cubic yard delivered. Small loads (under 4 yards) often incur a "short load fee."
- Labor: Professional finishing usually costs between $4 and $8 per square foot, depending on the complexity (stamping, staining, or reinforced edges).
- Reinforcement: Don't forget to budget for rebar or wire mesh, which adds strength and crack resistance.
- Grading & Base: A proper gravel base is essential for drainage and prevents the slab from cracking due to ground movement.
DIY vs. Professional Installation
If your project requires less than 1 cubic yard (approx. 45 bags of 80lb premix), it is often a manageable DIY project. However, for anything larger than a small walkway, ordering a ready-mix truck is often more economical and results in a stronger, more consistent cure. Mixing by hand is physically demanding and time-sensitive.
function calculateConcrete() {
// 1. Get DOM Elements matching IDs
var lengthInput = document.getElementById('slabLength');
var widthInput = document.getElementById('slabWidth');
var thickInput = document.getElementById('slabThickness');
var priceInput = document.getElementById('costPerYard');
var laborInput = document.getElementById('laborCost');
var wasteInput = document.getElementById('includeWaste');
var errorDiv = document.getElementById('errorDisplay');
var diyDiv = document.getElementById('diyInfo');
// 2. Parse values
var length = parseFloat(lengthInput.value);
var width = parseFloat(widthInput.value);
var thicknessInches = parseFloat(thickInput.value);
var pricePerYard = parseFloat(priceInput.value);
var laborPerSqFt = parseFloat(laborInput.value);
var wasteFactor = parseFloat(wasteInput.value);
// 3. Validation
if (isNaN(length) || isNaN(width) || length <= 0 || width <= 0) {
errorDiv.style.display = 'block';
return;
} else {
errorDiv.style.display = 'none';
}
if (isNaN(pricePerYard)) pricePerYard = 0;
if (isNaN(laborPerSqFt)) laborPerSqFt = 0;
// 4. Calculations
var sqFt = length * width;
var thicknessFeet = thicknessInches / 12;
var cubicFeet = sqFt * thicknessFeet;
var baseCubicYards = cubicFeet / 27;
// Apply waste factor
var totalCubicYards = baseCubicYards * wasteFactor;
// Cost Calculations
var materialCost = totalCubicYards * pricePerYard;
var laborTotal = sqFt * laborPerSqFt;
var grandTotal = materialCost + laborTotal;
// DIY Bag Calculations (for pre-mix concrete)
// Approx 0.6 cubic feet per 80lb bag, 0.45 per 60lb bag
var cubicFeetWithWaste = cubicFeet * wasteFactor;
var bags80 = Math.ceil(cubicFeetWithWaste / 0.6);
var bags60 = Math.ceil(cubicFeetWithWaste / 0.45);
// 5. Update UI
document.getElementById('resArea').innerText = sqFt.toLocaleString('en-US', {maximumFractionDigits: 0}) + " sq ft";
document.getElementById('resVolume').innerText = totalCubicYards.toFixed(2) + " cu yds";
document.getElementById('resMatCost').innerText = "$" + materialCost.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resLabor').innerText = "$" + laborTotal.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTotal').innerText = "$" + grandTotal.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
// Show DIY info if volume is small (less than 2 yards)
if (totalCubicYards < 2) {
diyDiv.style.display = 'block';
document.getElementById('resBags80').innerText = bags80;
document.getElementById('resBags60').innerText = bags60;
} else {
diyDiv.style.display = 'none';
}
}