How many bags of concrete for a 10×10 slab?
Quick Answer
A 10×10 foot slab poured 4 inches thick requires 1.23 cubic yards of concrete, or approximately 56 bags of 80-lb mix (each covers 0.022 yd³). For a 6-inch slab, you need 1.85 cubic yards — about 84 bags of 80-lb mix. For slabs over 1 yard, ready-mix is more economical than bags.
Quick Reference Table
| Slab Size (4" thick) | 80-lb Bags Needed |
|---|---|
| 4×4 ft | 9 bags |
| 6×6 ft | 20 bags |
| 10×10 ft | 56 bags |
| 12×12 ft | 80 bags |
| 10×20 ft | 111 bags |
| 20×20 ft | 222 bags |
How to Calculate It Yourself
- 1
Calculate cubic feet: length × width × depth (in feet). For 10×10 at 4": 10 × 10 × 0.333 = 33.3 cubic feet.
- 2
Convert to cubic yards: 33.3 ÷ 27 = 1.23 cubic yards.
- 3
Add 10% waste: 1.23 × 1.10 = 1.35 cubic yards to order.
- 4
Convert to bags: one 80-lb bag = 0.022 yd³. So 1.35 ÷ 0.022 = 61 bags. Round up to 62.
Pro Tip
Above 1 cubic yard, ready-mix concrete is almost always cheaper than bags. Bags run $6–9 each at retail — 56 bags = $336–504 just in materials. A yard of ready-mix costs $150–175 delivered. For a 10×10 slab, ready-mix saves $100–200 and saves hours of mixing.
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