Sack Concrete Calculator

Sack Concrete Calculator

80 lb Sack (0.60 cu ft yield) 60 lb Sack (0.45 cu ft yield) 40 lb Sack (0.30 cu ft yield)

Results

Total Volume: 0 Cubic Feet

Total Cubic Yards: 0 Cubic Yards

Total Sacks Required: 0 Bags

function calculateSacks() { var length = parseFloat(document.getElementById('calcLength').value); var width = parseFloat(document.getElementById('calcWidth').value); var thickness = parseFloat(document.getElementById('calcThickness').value); var bagSize = document.getElementById('calcBagSize').value; var waste = parseFloat(document.getElementById('calcWaste').value); if (isNaN(length) || isNaN(width) || isNaN(thickness) || length <= 0 || width <= 0 || thickness <= 0) { alert("Please enter valid positive numbers for dimensions."); return; } if (isNaN(waste)) { waste = 0; } // Calculate Volume in Cubic Feet // Thickness in inches / 12 = thickness in feet var volumeCF = length * width * (thickness / 12); // Apply waste factor var totalVolumeCF = volumeCF * (1 + (waste / 100)); // Cubic Yards (1 yard = 27 cubic feet) var volumeCY = totalVolumeCF / 27; // Bag Yields (Approximate standards) var yieldPerBag = 0; if (bagSize === "80") { yieldPerBag = 0.60; } else if (bagSize === "60") { yieldPerBag = 0.45; } else if (bagSize === "40") { yieldPerBag = 0.30; } var totalBags = Math.ceil(totalVolumeCF / yieldPerBag); document.getElementById('resVolume').innerText = totalVolumeCF.toFixed(2); document.getElementById('resYards').innerText = volumeCY.toFixed(3); document.getElementById('resSacks').innerText = totalBags; document.getElementById('concreteResults').style.display = 'block'; }

Understanding Your Concrete Sack Requirements

Planning a DIY project like a new garden path, a small patio, or post footings requires an accurate estimate of how many concrete sacks to purchase. Underestimating means making another trip to the hardware store mid-pour, while overestimating leaves you with heavy, moisture-sensitive bags that are difficult to store.

How Concrete Volume is Calculated

Concrete is measured by volume. To find the amount you need, you multiply Length x Width x Thickness. Since most projects are measured in feet for surface area but inches for depth, our calculator automatically handles the conversion. A standard 4-inch slab is the benchmark for residential sidewalks and patios, while 6 inches is recommended for driveways.

Standard Sack Yields

Pre-mixed concrete bags typically come in three common sizes. Their coverage depends on the density and mix design, but the following industry standards apply:

• 80 lb Bag: Yields approximately 0.60 cubic feet of wet concrete.
• 60 lb Bag: Yields approximately 0.45 cubic feet of wet concrete.
• 40 lb Bag: Yields approximately 0.30 cubic feet of wet concrete.

Practical Example: A Small Patio

If you are pouring a patio that is 10 feet long, 10 feet wide, and 4 inches thick, here is the math breakdown:

1. Convert Thickness to Feet: 4 inches / 12 = 0.33 feet.
2. Calculate Volume: 10′ x 10′ x 0.33′ = 33.33 cubic feet.
3. Add Waste (10%): 33.33 x 1.10 = 36.66 cubic feet.
4. Determine Bags (80 lb): 36.66 / 0.60 = 61.1 bags. Round up to 62 bags.

The Importance of the Waste Factor

We recommend a minimum waste factor of 10%. This accounts for variations in the subgrade (if the ground isn't perfectly level), spillage during mixing, and material left inside the mixer or wheelbarrow. For post holes, consider increasing the waste factor to 15% due to the irregular shapes of excavated soil.