How Many Bags of Concrete for a 7x7 Slab?
Small pads like a 7x7 suit bagged mix. How many bags of concrete for a 7x7 slab at a standard 4-inch depth: 28 × 80 lb, or 37 × 60 lb, since each bag yields only about 0.6 or 0.45 cubic feet.
Concrete calculator →How the bag count is figured
- Area: 7 × 7 = 49 sq ft.
- Volume at 4 in: 49 × 0.333 = 16.33 cu ft.
- 80 lb bags: 16.33 ÷ 0.60 = 27.2, round up to 28.
- 60 lb bags: 16.33 ÷ 0.45 = 36.3, round up to 37.
Check the yield printed on your brand’s bag, since it varies a little. The concrete calculator handles other shapes.
Related: How Many Bags of Concrete for a 10x10 Slab?
Bags by thickness for a 7x7 slab
| Thickness | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|
| 3 in | 12.25 | 21 | 28 | 41 |
| 4 in | 16.33 | 28 | 37 | 55 |
| 5 in | 20.42 | 35 | 46 | 69 |
| 6 in | 24.50 | 41 | 55 | 82 |
Is bagged mix the right call?
Bags win on small pads because there is no delivery or short-load charge. The tradeoff is labor: 28 bags of 80 lb mix is 2,240 pounds to lift, pour and mix. A small drum mixer keeps batches consistent, and a helper keeps the pour moving so the edges do not set before the middle.
Related: How Many Bags of Concrete for an 8x10 Slab?
Prep for a small slab
Dig out sod and soft soil, compact the bottom and add a few inches of compacted gravel. Set 2x4 forms level or with a slight slope for drainage, stake them every couple of feet and check the diagonals so the pad is square. Mixing 28 bags takes time, so stage them next to the forms before you start.
Buying the bags
A pallet of 80 lb bags often holds around 40 to 42 bags, so this job is about 1 pallet or less. Buy one or two extra bags: returning an unopened bag is easier than running out mid-pour.
Questions people ask
How many 80 lb bags for a 7x7 slab?
About 28 bags at 4 inches thick.
How many 60 lb bags for a 7x7 slab?
About 37 bags at 4 inches thick.
How many bags for a 7x7 slab 6 inches thick?
About 41 bags of 80 lb mix or 55 of 60 lb.
How much does an 80 lb bag of concrete yield?
About 0.6 cubic feet of mixed concrete.
How thick should the base under the slab be?
About 4 inches of compacted gravel is common for residential slabs, more on soft or poorly drained soil.
Related guides
- How Much Area Does a Yard of Concrete Cover?
- How Many Bags of Concrete in a Yard? 40, 60, 80 lb
- Gravel Base Under a Concrete Slab: Depth and Tons
- How Many Yards in a Concrete Truck? Mixer Sizes
- Concrete Short Load Fee: What It Is and How to Cut It
- 60 lb vs 80 lb Concrete Bags: Yield, Count, and Cost
- Rebar vs Wire Mesh in a Slab: Which One to Use
- How Many Bags of Concrete for a 5x8 Slab?
- How Many Bags of Concrete for a 6x10 Slab?
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