Concrete Calculator
Calculate concrete volume in cubic feet and cubic yards, 60-lb and 80-lb bag counts, ready-mix truck costs, and waste allowance.
Calculation Results
Concrete Volume Formula
Cubic Feet = Length (ft) × Width (ft) × (Thickness (in) / 12) | Cubic Yards = Cubic Feet / 27- Volume Conversion: 27 cubic feet = 1 cubic yard (3 ft × 3 ft × 3 ft).
- 80-lb Bag Yield: Approximately 0.60 cubic feet (45 bags per cubic yard).
- 60-lb Bag Yield: Approximately 0.45 cubic feet (60 bags per cubic yard).
- Waste Factor: Standard 10% allowance to compensate for uneven excavation and spillage.
Step-by-Step Worked Example
Calculation Steps:
- Cubic Feet = 24 × 12 × (4 / 12) = 96.00 cu ft
- Cubic Yards = 96.00 / 27 = 3.56 cu yd
- Cubic Yards with 10% Waste = 3.56 × 1.10 = 3.91 cu yd (105.6 cu ft)
- 80-lb Bags Needed = 105.6 / 0.60 = 176 bags
- Ready-Mix Truck Cost = 3.91 cu yd × $145 = $567
- Bagged Cost = 176 bags × $7.25 = $1,276
How to Use This Calculator
- 1Enter length and width in feet, and slab thickness in inches.
- 2Include 10% waste for ground unevenness and edge forms.
- 3Compare bagged costs against ready-mix truck delivery.
Assumptions & Limitations
- Estimates are based on standard national averages and current prevailing construction materials and contractor rates.
- Actual trade bids may fluctuate according to local building code requirements, permit fees, and site topography.
- Always obtain multiple written bids from licensed, bonded, and insured contractors before commencing work.
Frequently Asked Questions
When should I order a concrete truck instead of buying bags?
Generally, any project requiring more than 1.5 to 2 cubic yards (approx. 70 to 90 80-lb bags) is much faster, structurally stronger, and more cost-effective when delivered by a ready-mix truck.
How thick should a typical concrete driveway or patio be?
Patios and walkways are typically 4 inches thick (3,500 PSI). Driveways supporting passenger vehicles should be at least 4 to 5 inches thick with rebar or wire mesh reinforcement.
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