Slab Volume Calculator
Easily calculate the volume and concrete needed for your slab project.
Cost Estimation (Optional)
How to use Slab Volume Calculator
Using our calculator is straightforward. Follow these simple steps for an accurate measurement:
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Measure Dimensions: Carefully measure the length, width, and desired thickness of your concrete slab.
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Select Units: Enter your measurements into the calculator and select the correct unit (feet, inches, etc.) for each dimension.
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Input Cost (Optional): If you want a budget estimate, enter the price per cubic yard for concrete and any labor costs.
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Calculate: Click the "Calculate Now" button to see the total volume, number of bags needed, and the estimated cost.
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Formulas Used in This Calculator
1. Slab Volume Calculation
The total volume is calculated by multiplying the slab's length, width, and thickness after converting all measurements to feet.
Volume (ft³) = Length (ft) × Width (ft) × Thickness (ft)
2. Volume Unit Conversion
The volume in cubic feet is converted to other common units for ordering ready-mix concrete or for international use.
Volume (yd³) = Volume (ft³) / 27
Volume (m³) = Volume (ft³) × 0.0283168
3. Concrete Bag Calculation
The number of bags is found by dividing the total slab volume by the concrete yield per bag.
Number of Bags = Total Volume (ft³) / Bag Yield (ft³)
Yields: 80lb ≈ 0.6 ft³, 60lb ≈ 0.45 ft³, 40lb ≈ 0.3 ft³
How to Use & Example Calculation
1. Enter Dimensions
Input the length, width, and thickness of your slab. You can use different units (feet, inches, meters) for each measurement.
2. Add Costs (Optional)
For a full budget, enter your local cost per cubic yard of concrete and any additional labor costs.
3. Calculate & Review
Click "Calculate Now" to get an instant breakdown of the required materials and total estimated cost.
Example: Patio Specs
Imagine a patio that is 12 ft long, 10 ft wide, and 4 inches thick. We'll use these values for our calculation.
Example: Volume Math
First, convert thickness to feet (4/12 = 0.333). Then, multiply: 12 ft × 10 ft × 0.333 ft = 40 ft³.
Example: Final Amount
The total volume is 1.48 yd³ (40/27) for a truck order, or about 89 of the 60 lb concrete bags.
Key Features & Advantages
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Flexible Units: Mix and match feet, inches, and meters. The calculator handles all conversions for you.
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Bag or Bulk Estimates: Get results in cubic yards for ready-mix trucks or by bag count for smaller DIY jobs.
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Budget Planning: Instantly see your estimated material and labor costs to stay on budget.
Pro Tips for Pouring Slabs
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Order 10% Extra: Always order about 10% more concrete than calculated to account for uneven subgrade and spillage.
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Prepare the Sub-base: A level, compacted base of gravel is crucial for a stable, crack-free slab.
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Cure Properly: Keep new concrete moist for several days by covering it. This is vital for reaching maximum strength.
Frequently Asked Questions
How thick should a concrete slab be?
It depends on the use: 4 inches is standard for patios and walkways. A driveway for cars should be at least 5-6 inches thick. A foundation for a shed or garage might be 4-6 inches, but always check local building codes.
Do I need rebar for my patio slab?
For a standard 4-inch patio, wire mesh is often sufficient to prevent cracking. For thicker slabs or those on unstable soil, a grid of #3 or #4 rebar provides superior strength. Driveways always require rebar.
What is the difference between cubic feet and cubic yards?
They are both units of volume. There are 27 cubic feet in 1 cubic yard (3ft x 3ft x 3ft). Ready-mix concrete is sold by the cubic yard, while bagged concrete calculations often start with cubic feet.
How much does a cubic yard of concrete cost?
Prices vary significantly by location, but typically range from $125 to $175 per cubic yard. There may also be delivery fees or short-load fees for orders under a certain volume.
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