Concrete Slab Calculator
Calculate cubic yards, cubic feet, and bags needed for a concrete slab.
This concrete slab calculator will help you estimate the cubic yards, truckloads, and bags of concrete you'll need. It also includes a rebar estimate, a 10% waste factor (which can be adjusted), and the cost of the concrete if pricing is provided.With Houzz Pro software, you can pull up pre-priced material costs from our built-in Cost Catalog or use the Clipper tool to save products and prices from your preferred vendor websites.
How much concrete do I need?
The amount of material you need for a concrete slab is determined by the volume of the slab (measured in cubic feet), your waste allowance, and whether you’re getting your concrete from a truck or using 60- or 80-pound bags.To calculate the cubic yards of concrete needed to pour a slab, multiply the area of the slab (length x width) by the thickness and divide the result by 27 (the number of cubic feet in a cubic yard). You’ll need to convert the thickness to feet by dividing it by 12 (ex. 4 inches equals 0.33 feet).Cubic yards of concrete = length x width x thickness / 27
To add a waste factor of 10-15%, multiply the result by 1.1 or 1.15.Standard concrete trucks hold 10 cubic yards of concrete, so divide the amount of concrete you need by 10 to determine how many trucks it will take.Number of concrete trucks = cubic yards of concrete / 10
If you’re using bagged concrete, a 60-pound bag yields approximately 0.017 cubic yards, and an 80-pound bag makes 0.022 cubic yards. Divide the concrete amount by the per-bag yield to determine how many bags you’ll need.Number of concrete bags = cubic yards of concrete / bag yield
Concrete slab calculation example
Here’s an example of a concrete slab calculation using these formulas:- Length: 12 feet
- Width: 10 feet
- Thickness: 4 inches
- Quantity: 1
- Waste factor: 10%
- Cubic yards of concrete = 12 x 10 x 0.33 / 27 = 1.46
- Add waste = 1.46 x 1.10 = 1.62
- Truck = 1
- 60-pound bags = 1.62 / 0.017 = 96
- 80-pound bags = 1.62 / 0.022 = 74
Concrete slab, concrete bag, and rebar calculator
Our concrete slab calculator will help you determine the cubic feet, cubic yards, ready-mix trucks, bags, and rebar you’ll need. It’ll also calculate the cost of the concrete if you provide a price, saving you time when estimating work.- Enter the following into the calculator:
- Length of the slab in feet
- Width of the slab in feet
- Thickness of the slab in inches
- Quantity of slabs
- Waste factor (at least 10%)
- Price per cubic yard for concrete (optional)
- Click Calculate, and you’ll receive all the information you need to estimate costs for pouring a concrete slab, including cubic feet and yards, number of trucks, bags of concrete, and length of rebar.
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