Concrete Slab Calculator
Estimate exactly how much concrete your slab needs. Enter the dimensions and thickness below to see the volume in cubic feet and cubic yards, the number of pre-mixed bags for small pours, and a ballpark cost for ready-mix delivery.
Updated June 2026 · Free · No sign-up
Your project
Estimate
Concrete needed · Order this much ready-mix
- Volume
- 33.3ft³
- 80 lb bags (small pours)
- 56bags
- Estimated material cost
- $160.49
Estimates are guidance only and exclude tax, labor, and site conditions unless stated. Confirm with a local pro.
How it's calculated
No black boxes — here is the exact math behind your estimate, so you can check it or adapt it for your own quote.
- 1
Volume (ft³) = length × width × (thickness ÷ 12) - 2
Cubic yards = volume (ft³) ÷ 27 - 3
Bags (80 lb) = ⌈ volume (ft³) ÷ 0.6 ⌉ - 4
Cost = cubic yards × price per yard
Worked example
A 10 ft × 10 ft patio slab poured 4 inches thick.
Inputs
- Length
- 10 ft
- Width
- 10 ft
- Thickness
- 4 in
- Ready-mix price
- 130 $/yd³
Result
- Concrete needed
- 1.23 yd³
- Volume
- 33.3 ft³
- 80 lb bags (small pours)
- 56 bags
- Estimated material cost
- $160.49
Compare local pros for concrete slab
An estimate gets you a budget. A few competing quotes get you the real price. Tell us about the job and we'll help you find vetted contractors nearby.