How Many Bags of Concrete for a 10×10 Slab?
Short answer: a 10 × 10 ft slab 4 in thick is 33.3 cu ft, about 1.23 cubic yards. That's 56 bags of 80 lb or 75 bags of 60 lb, plus your waste allowance.
The math, step by step
Concrete volume is length × width × thickness, with every number in feet. A 4 in slab is 4 ÷ 12 = 0.333 ft thick, so a 10 × 10 slab is 10 × 10 × 0.333 = 33.3 cubic feet. Divide by 27 (cubic feet in a cubic yard) and you get 1.23 cubic yards.
Premixed bags are labelled with how much concrete each one makes. Typical yields are about 0.60 cu ft for an 80 lb bag, 0.45 cu ft for 60 lb and 0.30 cu ft for 40 lb. Divide the volume by the yield and round up:
- 80 lb: 33.3 ÷ 0.60 = 55.6 → 56 bags
- 60 lb: 33.3 ÷ 0.45 = 74.1 → 75 bags
- 40 lb: 33.3 ÷ 0.30 = 111.1 → 112 bags
Most people add 5–10% for an uneven base, spillage and forms that bow out a little. With 10% extra, a 4 in 10 × 10 slab becomes 36.7 cu ft: 62 bags of 80 lb or 82 bags of 60 lb.
10×10 slab chart by thickness
| Thickness | Cu ft | Cu yd | 80 lb bags | 60 lb bags | 80 lb +10% |
|---|---|---|---|---|---|
| 3.5 in | 29.2 | 1.08 | 49 | 65 | 54 |
| 4 in | 33.3 | 1.23 | 56 | 75 | 62 |
| 5 in | 41.7 | 1.54 | 70 | 93 | 77 |
| 6 in | 50.0 | 1.85 | 84 | 112 | 92 |
Bag counts are rounded up and use the typical yields above. Check the yield printed on your brand's bag.
Is bagged concrete realistic for 1.2 yards?
Fifty-plus 80 lb bags is more than two tons of material to lift, mix and place, and it all needs to go down before the first batches start to set. It's doable with a rented mixer and a few helpers, especially if you pour in sections with control joints. Many people find that around this size a ready-mix delivery (ask about short-load fees) or a mixer trailer from the supplier is worth pricing. Compare both with the cost fields in the concrete calculator.
Before you pour
- Measure the formed area, not the planned one. Forms that end up 10' 3" change the numbers.
- Check the base depth in several spots. A low corner can quietly eat several bags.
- Ask your local building department whether the slab needs a permit, reinforcement or a particular thickness.
Related
- Concrete calculator (slabs, footings, columns)
- How many bags of concrete in a yard
- Concrete for fence posts
- Gravel calculator for the slab base
FAQ
How many 80 lb bags of concrete for a 10x10 slab?
At 4 in thick, 56 bags (33.3 cu ft ÷ 0.60 cu ft per bag), or 62 bags with 10% extra.
How many 60 lb bags for a 10x10 slab?
At 4 in thick, 75 bags (33.3 ÷ 0.45), or 82 with 10% extra.
How many yards of concrete is a 10x10 slab?
1.23 cubic yards at 4 in thick, 1.54 at 5 in and 1.85 at 6 in.