Concrete Slab & Footing Calculator
0% (Exact)
5% (Recommended)
10% (Safe)
Estimation Results
Total Volume Needed:
0 Cubic Yards
Estimated Cost:
$0.00
60lb Pre-Mix Bags:
0
80lb Pre-Mix Bags:
0
*Includes selected safety margin.
How to Calculate Concrete Volume
Whether you are pouring a slab for a shed, a driveway, or a patio, accurately calculating the amount of concrete needed is crucial to avoid running short mid-pour or overspending on materials. This calculator helps determine the cubic yardage required based on standard measurements.
The Concrete Formula
To calculate the concrete needed for a slab, you need to find the volume in cubic feet and convert it to cubic yards (since concrete is sold by the yard). The formula is:
- Step 1: Convert thickness from inches to feet (Inches ÷ 12).
- Step 2: Multiply Length (ft) × Width (ft) × Thickness (ft) = Cubic Feet.
- Step 3: Divide Cubic Feet by 27 = Cubic Yards.
Pre-Mixed Bags vs. Ready-Mix Truck
For smaller projects (typically under 1-2 cubic yards), buying pre-mixed bags (60lb or 80lb) from a hardware store is often more economical. For larger projects, ordering a ready-mix truck is standard. This tool calculates both so you can compare:
- 80lb bag: Yields approximately 0.60 cubic feet.
- 60lb bag: Yields approximately 0.45 cubic feet.
Why Include a Safety Margin?
It is industry standard to order 5% to 10% more concrete than your exact mathematical calculation. This accounts for:
- Spillage during the pour.
- Uneven subgrade (dips in the ground).
- Settling of forms.
Our calculator allows you to select a 5% or 10% buffer to ensure you don't run out.