Concrete Slab & Footing Calculator
80 lb bags
60 lb bags
50 lb bags
40 lb bags
Estimation Results
Total Volume (Cubic Yards):
0
Total Volume (Cubic Feet):
0
Pre-mix Bags Needed (80lb):
0
Estimated Material Cost (Bulk):
$0.00
How to Calculate Concrete for Your Project
Planning a driveway, patio, or foundation footing requires precise calculations to ensure you order enough concrete without overspending. Concrete is measured by volume, typically in cubic yards for bulk orders or by the number of pre-mix bags for smaller DIY projects.
The Concrete Formula
The basic formula for a concrete slab is:
Length (ft) × Width (ft) × Thickness (ft) = Cubic Feet
Since concrete is sold by the Cubic Yard, you divide the cubic feet by 27 (since there are 27 cubic feet in one cubic yard). Our calculator handles these conversions automatically, including the conversion of thickness from inches to feet.
Why Factor in Waste?
Professional contractors always add a safety margin, typically 5% to 10%. This accounts for:
- Spillage during transport or pouring.
- Uneven subgrade (the ground beneath the concrete) which may require more depth in spots.
- Settling of the forms.
Standard Thickness Guide
- 4 Inches: Standard for residential sidewalks, patios, and garage floors (for passenger cars).
- 5-6 Inches: Recommended for driveways holding heavier vehicles (trucks, RVs).
- 6+ Inches: Heavy-duty commercial loads.
Pre-mix Bags vs. Ready Mix Truck
If your project requires less than 1 cubic yard (about 45 of the 60lb bags or 34 of the 80lb bags), it is often more economical to mix it yourself using bags. For volumes over 1-2 cubic yards, ordering a ready-mix truck is usually cheaper and ensures a more consistent pour.