How to use this calculator
- Enter the slab dimensions. Input the length, width, and thickness of your pour. Most residential slabs are 4 inches thick.
- Pick your units. Toggle between feet, inches, yards, meters, or centimeters — the calculator converts everything internally.
- Add a waste allowance. Most pros order 5–10% extra to account for spills, uneven sub-grade, and leftover in the chute.
- Read your result. You get cubic yards (what ready-mix trucks deliver), cubic feet, cubic meters, and the equivalent number of 60 lb and 80 lb bags.
Formula
Volume (yd³) = Length × Width × Thickness ÷ 27
Worked example
A 10 ft × 12 ft × 4 in slab equals 0.4 cubic yards (about 11 cubic feet). For one truck delivery you would order 0.5 yd³ minimum; if bagging you would need roughly 25 bags of 60 lb pre-mix or 19 bags of 80 lb pre-mix.
Common project sizes
Quick reference for the most common concrete calculator use cases. Use these as a sanity check on your calculator inputs.
| Project | Dimensions | Result |
|---|---|---|
| Sidewalk slab (3×20×4 in) | 60 ft² | 0.74 yd³ · 30 bags (80 lb) |
| Patio (10×12×4 in) | 120 ft² | 1.48 yd³ · 60 bags (80 lb) |
| One-car driveway (10×20×4 in) | 200 ft² | 2.47 yd³ · 100 bags (80 lb) |
| Two-car garage slab (24×24×4 in) | 576 ft² | 7.11 yd³ · ready-mix only |
| Footing run (1×1×30 ft) | 30 ft³ | 1.11 yd³ · 45 bags (80 lb) |
2026 cost reference
Typical retail price range in the United States for concrete. Local pricing varies by region, supplier, and grade — confirm with two or three quotes before ordering.
Per cubic yard (delivered ready-mix)
$125 – $175
3,000 PSI residential mix is $125–$155/yd³ in most US markets. Higher-strength (4,000+ PSI) or fiber-reinforced mixes add $10–$25/yd³. Add a $80–$200 short-load fee for orders under 3 yd³, and $5–$15 per minute of standby if your prep is not ready when the truck arrives. Bagged 80 lb pre-mix is $4–$6/bag — roughly 45 bags = $200 for one yard equivalent, plus your time mixing.
By the numbers — regional pricing
Snapshot of current US pricing for cubic yard (delivered 3,000 psi ready-mix), broken down by Census region. Source: BLS Producer Price Index series PCU3273203273201 (ready-mix concrete) + regional supplier spot-checks across 12 metros. Data as of April 2026; we refresh quarterly.
| Region | Low | High | Note |
|---|---|---|---|
| Northeast | $155 | $195 | Boston, Philadelphia, NYC: higher floor due to permit-driven schedule premiums. |
| Midwest | $130 | $165 | Chicago, Detroit, Minneapolis: most competitive plant density. |
| South | $125 | $160 | Atlanta, Dallas, Houston: lowest base price; subject to summer scheduling delays. |
| West | $145 | $210 | Seattle, Bay Area, LA: highest variance — coastal markets price 25–40% above inland. |
How we calculate this
Assumptions baked in
The calculator computes ready-mix volume as Length × Width × Thickness ÷ 27, returning cubic yards. Bag conversions assume the manufacturer-published yield for Quikrete / Sakrete pre-mix: 0.45 ft³ per 60 lb bag and 0.60 ft³ per 80 lb bag. We round bag counts UP and add a 5–10% pour waste cushion in the displayed total — the actual waste in your project depends on form bow, sub-grade levelness, and how full the chute leaves on the last truck. Density assumed: 150 lb/ft³ for normal-weight concrete, consistent with ACI 318 §19.2.4.1.
Accuracy and margin of error
For rectangular slabs and footings, the volume formula is exact (±0). Bag yield varies up to 5% between manufacturers and lots — order one extra bag on jobs below 0.5 yd³, and order at the next 0.25 yd³ increment up on ready-mix deliveries. Cubic-meter and cubic-foot conversions use the exact factors 1 yd³ = 0.7646 m³ = 27 ft³; rounding shows two decimals so the order quantity is unambiguous at the supplier.
Edge cases this calculator does not handle
Curved or irregular shapes: split into rectangles, run each through the calculator, then sum. Sloped slabs and step-downs: use the average thickness — for a slab that slopes from 4" at the door to 6" at the apron, enter 5". Pours below 50°F or above 90°F need a different mix design (Type I/II + accelerator or retarder); the calculator returns volume correctly but you should call your ready-mix dispatcher to spec the mix.
Cited sources for this page
The figures and rules above are anchored to the following normative references. We link the underlying claim to its standard — not as generic SEO trust signals, but so you can audit any number on this page against a primary source.
Normal-weight concrete density of 150 lb/ft³ is the reference value in ACI 318 §19.2.4.1.
Source: ACI 318-19 Building Code Requirements for Structural Concrete
A 4-inch slab thickness with #3 rebar or 6×6 W1.4 welded wire mesh is the IRC minimum for residential floors on ground.
Concrete reaches roughly 70% of design strength at 7 days and 99% at 28 days under standard curing.
Tips for accurate results
- Order 5–10% extra. A short load is far more expensive than a few wasted dollars of concrete.
- Below-grade and structural slabs typically use a higher PSI mix (3,500+) than a sidewalk (3,000 PSI).
- For very small jobs, bagged pre-mix is cheaper than a short-load fee — break-even is usually around 0.5 yd³.
- Don't pour against frozen ground; cure above 50°F for at least 24 hours.
Common mistakes to avoid
- Forgetting the short-load fee — most plants charge $80–$200 extra on orders under 3 yd³, which can wipe out the per-yard savings versus bagged.
- Pouring on dry, dusty subgrade — wet the soil first or the slab will crack from moisture loss in the first 24 hours.
- Skipping control joints. Slabs over 100 ft² need joints every 8–12 feet, sawed to ¼ of the slab thickness, within 6–18 hours of pouring.
- Buying calculator-exact volume with no waste — every pour over 0.5 yd³ ends up needing extra for the chute, the wheelbarrow, and the inevitable form bow.
When to consult a pro
Bagged pours under 0.5 yd³ (footing for a fence, a small step) are well within DIY range. Anything from 0.5 to 2 yd³ is the awkward middle — bagging takes a full weekend and a mortar mixer rental, while a short-load fee makes ready-mix expensive per yard. Above 2 yd³, always go ready-mix. Hire a finisher for any visible slab over 100 ft² (broomed, exposed-aggregate, or stamped finishes are skill-dependent and a redo means demolition) and any structural pour with rebar tied to footings.