How to use it
- Enter length in feet.
- Enter width in feet.
- Enter thickness in inches.
- Read cubic yards, cubic feet, and bag count.
Your slab’s size determines how much concrete you’ll need, and over‑ordering costs money while under‑ordering delays projects. This free calculator takes the length, width, and thickness you enter, converts the dimensions to cubic feet, then to cubic yards (27 ft³ = 1 yd³) and finally divides the cubic‑foot total by 0.6 ft³ per 80‑lb bag. The result shows three clear numbers: total cubic yards for ordering bulk, total cubic feet for precise planning, and the approximate number of 80‑lb bags to purchase. No guesswork, no hidden fees—just instant, accurate data you can trust when ordering concrete for patios, driveways, or foundations. You can also adjust the numbers for a 5% waste factor or round up to the nearest full bag to ensure you have enough material on site. The calculator works for any shape that can be described by length, width, and uniform thickness, making it ideal for DIY homeowners and contractors alike.
Pro tips
- Add a 5‑10% waste allowance to cover spillage and uneven sub‑grade.
- Round up bag count to the next whole bag; you can’t buy a fraction of a bag.
- Order concrete a day early to avoid delivery delays.
- Double‑check thickness; a small error dramatically changes volume.
Real-life examples
- Homeowner planning a 200‑sq‑ft patio with 4‑in thickness.
- Contractor estimating concrete for a 30‑ft driveway slab.
- DIYer figuring material for a raised garden bed foundation.
Case study
Mike needed a 12 ft × 10 ft patio 4 in thick. Using the calculator he saw the job required 1.78 yd³, 48 ft³, and about 80 bags. He ordered exactly that amount, avoided a $150 over‑order and finished on schedule.