Concrete Slab & Footing Calculator
Estimate concrete volume in cubic yards/meters and 60lb/80lb premix bags required
m
m
in
%
Calculation Result
Concrete Volume Required
6.71 m³
8.77 cubic yards with 10% waste includedLoading visualization...
80-lb Bags
395
60-lb Bags
527
Cubic Yards
8.77
How this calculator works
1
Enter length, width, and slab thickness (e.g. 4 inches / 10 cm).
2
Specify wastage percentage allowance (default 10%).
3
Get cubic yards, cubic meters, and number of standard premix bags needed.
Formula & Mathematics
Concrete Volume & Bags Formula
Volume = (L × W × Thickness) × (1 + Wastage%); Bags = Yards³ × 45 (for 80-lb bags)
Includes industry-standard 10% allowance for spillage, subgrade unevenness, and forms.
Worked Example
12 ft × 10 ft patio slab with 4 inch thickness
L = 12 ft, W = 10 ft, Thickness = 4 in (0.333 ft), 10% wastage.
• Net Volume = 12 × 10 × 0.333 = 40 cubic feet
• In Cubic Yards = 40 / 27 = 1.48 cu yd + 10% waste = 1.63 cu yd
• 80-lb bags needed = ~74 bags
Requires 1.63 cubic yards (or ~74 bags of 80-lb premix).
Frequently Asked Questions
Patios and walkways are typically 4 inches thick. Driveways handling heavy vehicles should be 5 to 6 inches thick with rebar.
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