Calculate concrete volume, weight, bag counts, and a 2026 cost estimate — from slab dimensions or a known yardage.
Quick answer: Multiply length × width × thickness in feet and divide by 27. A 10 × 10 ft slab at 4 inches thick needs (10 × 10 × 0.333) / 27 = 1.23 cubic yards, or about 55 bags of 80 lb mix with 10 percent overage. For pours over 1 to 2 yards, ready-mix delivery is usually cheaper than bags.
Ballpark, not gospel. This estimates volume and bags from the numbers you punch in — always check the bag label yields and confirm with your supplier before ordering.
| Bag size | Bags per yard | Yield per bag | Best for |
|---|---|---|---|
| 40 lb | 90 | 0.30 cu ft | Fence posts, tiny repairs |
| 50 lb | 72 | 0.375 cu ft | Small pads and repairs |
| 60 lb | 60 | 0.45 cu ft | Small slabs and posts |
| 80 lb | 45 | 0.60 cu ft | Small slabs and footings |
| 90 lb | 40 | 0.675 cu ft | Larger small pours |
Bag yields come from manufacturer data — an 80 lb bag yields about 0.60 cubic feet. Exact yields vary by mix, so check the bag label and always round up.
| Project | Size | 4 in thick | 6 in thick |
|---|---|---|---|
| Slab / patio | 10x10 | 1.23 | 1.85 |
| Driveway | 10x20 | 2.47 | 3.70 |
| Two-car driveway | 20x20 | 4.94 | 7.41 |
| Garage floor | 24x24 | 7.11 | 10.67 |
| Sidewalk | 4x50 | 2.47 | — |
Straight answers, no fluff. Then run your own numbers above.
Multiply slab length by width by thickness in feet, then divide by 27. Convert thickness from inches to feet first (4 inches = 0.333 feet).
A cubic yard takes about 45 bags of 80 lb concrete mix. Always round up because partial bags are not practical.
A cubic yard takes about 60 bags of 60 lb concrete mix. For larger work, ready-mix delivery is usually easier.
Many patios, sidewalks, and light slabs are 4 inches thick. Driveways and heavier slabs often use 5 to 6 inches or more.
Concrete weighs about 4,050 lbs per cubic yard. That is about 2.03 tons per cubic yard.
Bags work for small pours under about 1 to 2 cubic yards, like fence posts or small pads. Ready-mix delivery is usually cheaper and much faster for larger slabs, driveways, and footings.
A 24x24 ft slab at 4 inches thick needs about 7.11 cubic yards before overage. At 6 inches thick it needs about 10.67 yards. Add 10 percent extra in both cases.
A short-load fee ($50 to $200) is charged when you order less than a full truck, often under 4 yards. It covers the plant cost of running a partial truck, so small deliveries can cost more per yard.
Ready-mix concrete typically runs $125–$195 per cubic yard delivered in 2026, averaging around $130. The built-in cost estimator above prices your exact slab — enter your supplier's per-yard price, delivery fee, and tax.
Usually around 1 to 2 cubic yards. A yard of 80 lb bags costs roughly $150–$200 in bags alone (45 bags), while ready-mix at $130–$150/yard plus delivery often wins past 2 yards — and saves hours of mixing.
Yes. The material cost is priced on the overage-included order quantity, then delivery and tax are added — so the total reflects what you actually pay, not the raw math.
Converting between bags and yards? The concrete bag calculator goes both directions. Buying by the ton? The tons-to-yards converter handles the weight math, and the cubic yard cost guide breaks down 2026 delivered pricing.