Free Landscape Calculator

Concrete Calculator

Calculate exactly how many cubic yards and 80lb bags of concrete you need for slabs, driveways, patios and footings. Instant results with ready-mix and bag estimates.

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Concrete Calculator
Cubic yards, 80lb bags and cost
Dimensions
ft
ft
in
Common Thicknesses
📐 Your Results
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Cubic Yards
Ready-mix order
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80lb Bags
If mixing
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Cubic Feet
Volume
Estimated Cost
Avg. $100–$150/cubic yard
$—
💡 Always order 10–15% extra for waste and settling.

📊 Understanding Your Results

Cubic Yards — Standard unit for ready-mix concrete. Most companies have a 1 cubic yard minimum order.

80lb Bags — Each bag yields approximately 0.60 cubic feet. For small projects under 1 cubic yard, mixing bags yourself is practical.

Cost Estimate — Based on average US ready-mix prices of $100–$150 per cubic yard.

How the Concrete Calculator Works

Our concrete calculator uses standard volumetric calculations to estimate how much concrete you need for any slab, footing or structural pour.

The Concrete Formula

Step 1: Volume (cubic feet) = Length × Width × Thickness (all in feet)
Step 2: Cubic Yards = Cubic Feet ÷ 27
Step 3: 80lb Bags = Cubic Yards × 45
Step 4: Add 10% for waste, spillage and thickness variations

Example: A 10×20 ft driveway at 6 inches = 200 × (6÷12) = 100 cu ft = 3.7 cubic yards. Add 10% — order 4.1 yards.

Recommended Concrete Thickness by Application

ApplicationThicknessNotes
Sidewalk / walkway4 inchesFoot traffic only
Residential patio4 inchesFoot traffic, furniture
Garage floor4–6 inchesPassenger vehicles
Residential driveway4–6 inchesCars and light trucks
Heavy truck driveway6–8 inchesRV, delivery trucks

Frequently Asked Questions

Common questions about calculating concrete for slabs, driveways and patios.

How many cubic yards for a 10×10 slab at 4 inches?
100 × (4÷12) = 33.3 cu ft ÷ 27 = 1.23 cubic yards. Add 10% waste — order 1.4 cubic yards or approximately 56 bags of 80lb concrete.
How many 80lb bags of concrete equal a cubic yard?
One cubic yard = 27 cubic feet. An 80lb bag yields 0.60 cubic feet, so you need approximately 45 bags per cubic yard. At $6/bag = $270/yard vs $125/yard ready-mix.
How long does concrete take to cure?
Walkable after 24 hours, safe for vehicles after 7 days, full strength after 28 days. Keep moist for 7 days by covering with plastic — critical for full strength.
Do I need rebar in a concrete slab?
Yes for driveways and vehicle areas — use #4 rebar on 18-inch centers. For foot-traffic patios, wire mesh or fiber reinforcement is sufficient.
How much does ready-mix concrete cost per cubic yard?
Ready-mix costs $100–$200 per cubic yard. Standard 3,000 PSI mix averages $100–$150/yard. Short load fee: $50–$100 for orders under 3 yards.

💡 Pro Tips

Never under-order — running short mid-pour creates cold joints that weaken the slab.

Order on weekdays — Saturday delivery costs $50–$100 extra.

Keep concrete moist for 7 days after pouring for maximum strength.