How much concrete do you actually need?
Enter your slab's size and thickness and get a precise answer in bags or cubic yards — no sign-up, no guessing, no leftover half-mixed bag.
Quick reference: common slab sizes
Rough estimates at 4-inch thickness, 80 lb bags. Use the calculator above for your exact numbers.
| Slab size | Area | Volume | Bags (80 lb) |
|---|---|---|---|
| Small patio (8 × 8 ft) | 64 sq ft | 21.3 cu ft | 36 |
| Standard patio (10 × 10 ft) | 100 sq ft | 33.3 cu ft | 56 |
| Shed pad (12 × 10 ft) | 120 sq ft | 40 cu ft | 67 |
| Walkway (20 × 3 ft) | 60 sq ft | 20 cu ft | 34 |
| Single-car pad (12 × 20 ft) | 240 sq ft | 80 cu ft | 134 |
Common questions
How much concrete do I need for a 10x10 slab?
A 10×10 ft slab at the standard 4-inch thickness needs about 33.3 cubic feet of concrete, or roughly 1.23 cubic yards. In 80 lb bags, that's around 56 bags. Use the calculator above with your exact numbers for a precise figure.
How thick should a concrete slab be?
4 inches is standard for patios, walkways, and shed floors. Driveways for cars typically need 5–6 inches, and areas that will see heavier vehicle traffic may need more. Check your local building code for anything load-bearing or structural.
Should I order ready-mix or use bagged concrete?
Bagged concrete makes sense for small jobs — generally under 1 cubic yard — since mixing more than that by hand or with a small mixer gets impractical fast. For anything larger, a ready-mix truck ordered by the cubic yard is faster and usually cheaper per unit.
How many bags of concrete make a cubic yard?
It depends on bag size: about 45 bags of 60 lb concrete, or around 60 bags of 40 lb concrete, make one cubic yard. Bag yield varies slightly by brand, so check the yield printed on your specific bag and adjust if needed.