Part of the Construction collection — 4 tools available
Concrete Slab Calculator — How Much Concrete Do You Need?
Calculate how much concrete you need for your slab project. Estimate volume in cubic yards and total cost based on size, thickness, and price per yard.
About This Calculator
Planning a concrete slab for a patio, driveway, or shed foundation? Getting the right amount of concrete delivered is critical — order too little and you risk a cold joint that weakens the entire pour, order too much and you waste money on material that gets dumped on site. Ready-mix trucks charge by the cubic yard with minimum delivery fees, so accuracy pays off. Our concrete slab calculator takes your length, width, and thickness measurements and instantly estimates volume in cubic yards with a standard 10% waste allowance built in. It also shows estimated cost based on your supplier's per-yard price, so you can budget the pour with confidence before calling the dispatch office.
The Formula Behind This Calculator
Volume (cu ft) = Length * Width * (Thickness / 12) Volume (cu yd) = Volume (cu ft) / 27 Cost = Volume (cu yd) * Price per yard A 10% waste factor is added for spillage.
Understanding the math helps you verify results and make better decisions for your project.
Related Tools
How to Use
- 1Enter the length and width of your slab in feet.
- 2Specify the thickness in inches (4" for patios, 6" for driveways).
- 3Enter the price per cubic yard from your supplier quote.
- 4Click Calculate to get cubic yards needed and estimated cost.
When to Use
- →Estimating concrete before calling a ready-mix supplier for a delivery quote
- →Comparing costs between a DIY bag mix vs a delivered ready-mix order
- →Planning a shed foundation, patio, or driveway pour to budget materials accurately
Tips
- ✓Always add 10% extra for waste, spillage, and uneven ground — it's already built into this calculator
- ✓Order by the cubic yard for large projects; bagged concrete becomes impractical beyond 3-4 cubic yards
- ✓Schedule your pour early in the day so you have daylight to finish and cure the surface properly
FAQ
How thick should a concrete slab be?
Patios and walkways: 4 inches. Driveways: 6 inches. Heavy loads like RVs: 8 inches with rebar reinforcement.
How many bags of concrete equal a cubic yard?
About 45 bags of 80-lb premix per cubic yard. For slabs over a few square feet, ready-mix delivery is more practical and cost-effective.
Do I need rebar in my concrete slab?
For slabs 4"+ thick, especially driveways, use #3 or #4 rebar on 18" centers. Wire mesh works for thinner non-structural slabs.
How long does concrete take to cure?
Concrete reaches 70% strength in 7 days and full strength in 28 days. Keep it moist the first week for best results.
Related Calculators
Gravel Driveway Calculator — How Much Gravel Do You Need?
Estimate how many tons of gravel you need for a driveway. Enter length, width, depth, and price per ton to calculate coverage and total material cost.
Paint Calculator — How Much Paint Do You Need?
Figure out how many gallons of paint you need for any room. Accounts for walls, ceiling, doors, windows, and number of coats for an accurate estimate.
Flooring Calculator — How Much Flooring Do You Need?
Calculate how many boxes of flooring you need. Enter room dimensions and waste factor to estimate square footage, boxes, and total material cost.