Concrete Slab Cost Calculator
Enter your slab dimensions and a price per cubic yard to get the concrete volume you need, plus the delivered material cost with waste built in.
What your result means
The concrete cost is the volume of your slab, converted to cubic yards and bumped up 10% for waste, times your price per cubic yard. Slab volume is the raw size in cubic feet before waste. This figure is the ready-mix material only — forming, reinforcement, pouring, and finishing labor are separate.
How to use this calculator
- Measure the slab length and width in feet.
- Pick a thickness: 4 in for patios and walkways, 5-6 in for driveways and garages.
- Get a delivered price per cubic yard from your local ready-mix supplier.
- Read the concrete needed (waste included) and total material cost.
- Budget separately for forms, rebar or mesh, and finishing labor.
The formula
Multiply length by width by thickness in feet to get cubic feet, then divide by 27 for cubic yards. Add 10% for spillage and uneven subgrade, then multiply by your price per cubic yard.
Worked example
Say you're pouring a 20 by 20 ft patio at 4 in thick, with ready-mix at $160 a cubic yard. That's 133.3 cu ft, or 4.94 cubic yards. Add 10% waste and you're ordering about 5.43 yards, so the concrete runs roughly $869. Pouring and finishing labor would add another $1,600 to $2,400 at $4 to $6 a square foot.
Typical slab thickness and ready-mix pricing
| Use | Thickness | Notes |
|---|---|---|
| Walkway / patio | 4 in | Mesh or fiber mix is usually enough |
| Shed / small pad | 4 in | Compact the base well |
| Driveway | 5 - 6 in | Add rebar for heavy vehicles |
| Garage floor | 4 - 6 in | 6 in if parking trucks or equipment |
| Ready-mix delivered | — | Commonly $140 - $200 per cubic yard |
Tips & gotchas
- Order 10% extra. Running short mid-pour means a cold joint or a second delivery fee.
- Short-load fees apply under about 1 cubic yard — small pads can cost more per yard.
- A 4 in slab needs 81 sq ft per cubic yard; a 6 in slab only covers 54 sq ft per yard.
- Rebar, wire mesh, and a gravel base are extra and matter for crack resistance.
- This is material only. Forming and finishing labor usually doubles the total.
Frequently asked questions
How much does a concrete slab cost?
Material runs about $5 to $7 a square foot for a standard 4 in slab. With forming, rebar, and finishing labor, installed cost is usually $8 to $15 a square foot.
How many cubic yards do I need for a slab?
Multiply length by width by thickness in feet, divide by 27, then add 10% for waste. A 20 by 20 ft, 4 in slab needs about 5.4 yards with waste.
How thick should a concrete slab be?
4 inches for patios, walkways, and sheds; 5 to 6 inches for driveways and garages that carry vehicles.
Does the price include labor?
No. This calculator covers the ready-mix concrete only. Labor to form, pour, and finish typically adds $2 to $6 per square foot.
Why add 10% waste?
Subgrade is never perfectly level and some concrete is always lost to spillage and over-excavation. Ordering short is far more expensive than a little extra.
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Estimates only — see our full disclaimer.