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.
Assumptions to Check
Before ordering materials, confirm the dimensions, product coverage, waste factor, and local installation requirements for your project. Manufacturer coverage tables and local code rules can change the final quantity, especially for structural work, exterior projects, and irregular layouts.
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