Please enter valid positive numbers for all fields.
Total Area:0 sq. ft.
Volume Needed (incl. waste):0 cubic yards
Estimated Material Cost:0.00
Estimated Labor Cost:0.00
Total Estimated Project Cost:0.00
function calculateConcrete() {
// 1. Get Elements by ID
var lengthInput = document.getElementById('slabLength');
var widthInput = document.getElementById('slabWidth');
var thickInput = document.getElementById('slabThickness');
var wasteInput = document.getElementById('wasteFactor');
var priceInput = document.getElementById('pricePerYard');
var laborInput = document.getElementById('laborCost');
var errorDiv = document.getElementById('errorMsg');
var resultDiv = document.getElementById('resultsBox');
// 2. Parse Values
var length = parseFloat(lengthInput.value);
var width = parseFloat(widthInput.value);
var thicknessInches = parseFloat(thickInput.value);
var wastePercent = parseFloat(wasteInput.value);
var pricePerYard = parseFloat(priceInput.value);
var laborPerSqFt = parseFloat(laborInput.value);
// 3. Validation
if (isNaN(length) || length <= 0 ||
isNaN(width) || width <= 0 ||
isNaN(pricePerYard) || pricePerYard < 0 ||
isNaN(laborPerSqFt) || laborPerSqFt < 0) {
errorDiv.style.display = 'block';
resultDiv.style.display = 'none';
return;
}
errorDiv.style.display = 'none';
// 4. Calculation Logic
// Area in Square Feet
var areaSqFt = length * width;
// Volume in Cubic Feet = Area * (Thickness / 12)
var volumeCuFt = areaSqFt * (thicknessInches / 12);
// Volume in Cubic Yards = CuFt / 27
var volumeCuYards = volumeCuFt / 27;
// Add Waste Factor
var wasteMultiplier = 1 + (wastePercent / 100);
var totalYardsNeeded = volumeCuYards * wasteMultiplier;
// Round yards up to nearest 0.25 for ordering realism, but keep exact for cost math?
// Usually concrete is ordered in 0.5 or 0.25 increments. Let's just show 2 decimal places for accuracy.
// Costs
var materialCost = totalYardsNeeded * pricePerYard;
var laborCost = areaSqFt * laborPerSqFt;
var totalCost = materialCost + laborCost;
// 5. Update DOM
document.getElementById('resArea').innerText = areaSqFt.toFixed(0) + " sq. ft.";
document.getElementById('resVolume').innerText = totalYardsNeeded.toFixed(2) + " cubic yards";
document.getElementById('resMaterial').innerText = "$" + materialCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resLabor').innerText = "$" + laborCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTotal').innerText = "$" + totalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
resultDiv.style.display = 'block';
}
Understanding Concrete Slab Costs in 2024
Planning a new driveway, patio, or garage foundation requires accurate budgeting. Concrete is sold by volume (cubic yards), while labor is typically calculated by area (square feet). This calculator helps you bridge those two metrics to get a realistic estimate for your project.
How is Concrete Calculated?
To determine how much concrete you need, you must calculate the volume of the space. The formula used is:
(Length × Width × Thickness) ÷ 27 = Cubic Yards
Note that thickness must be converted to feet (inches ÷ 12) before multiplying. Our calculator handles this conversion automatically and divides by 27 (the number of cubic feet in a cubic yard).
Key Factors Affecting Your Cost
Thickness: A standard patio is usually 4 inches thick. However, a driveway intended to hold heavy vehicles should be at least 6 inches thick. Increasing thickness from 4″ to 6″ increases your material cost by 50%.
Waste Factor: It is standard industry practice to order 5-10% more concrete than the exact mathematical volume. This accounts for spillage, uneven subgrade depths, and ensuring you don't run out before the pour is finished.
Mix Strength: The price per yard can vary based on the PSI (pounds per square inch) rating. A 3000 PSI mix is standard for residential use, while 4000+ PSI is used for heavy loads.
Preparation & Labor: Often the most expensive part of a concrete project isn't the gray matter itself, but the labor. This includes excavation, grading, building forms, installing rebar or wire mesh, pouring, and finishing.
DIY vs. Professional Installation
While mixing concrete yourself (using bags) is feasible for very small pads (under 20 sq. ft.), ordering ready-mix via truck is necessary for larger slabs. For a standard 20×20 garage slab, you are dealing with nearly 40,000 lbs of wet concrete—a job that typically requires a professional crew to finish before it sets.