How Many Bags of Concrete for a 5x8 Slab?
How many bags of concrete for a 5x8 slab: about 23 bags of 80 lb mix at 4 inches thick, or 30 bags of 60 lb mix. The slab is 40 square feet, which at 4 inches is 13.33 cubic feet of concrete.
Concrete calculator →How the bag count is figured
- Area: 5 × 8 = 40 sq ft.
- Volume at 4 in: 40 × 0.333 = 13.33 cu ft.
- 80 lb bags: 13.33 ÷ 0.60 = 22.2, round up to 23.
- 60 lb bags: 13.33 ÷ 0.45 = 29.6, round up to 30.
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 5x8 slab
| Thickness | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|
| 3 in | 10.00 | 17 | 23 | 34 |
| 4 in | 13.33 | 23 | 30 | 45 |
| 5 in | 16.67 | 28 | 38 | 56 |
| 6 in | 20.00 | 34 | 45 | 67 |
Is bagged mix the right call?
Bags win on small pads because there is no delivery or short-load charge. The tradeoff is labor: 23 bags of 80 lb mix is 1,840 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?
Before you mix
A small slab still needs a firm base. Compact the soil, add compacted gravel and set forms to the finished height. If the pad will hold an AC unit, a generator or a grill, keep the top a little above the surrounding grade so water does not pool against it. Keep the fresh slab damp or covered for several days so it cures instead of drying out.
Buying the bags
Most stores stock 40, 60 and 80 lb bags. The 80 lb size means fewer bags to open, while 60 lb bags are easier to carry. Either way, buy a spare or two; a short pour is worse than a leftover bag.
Questions people ask
How many 80 lb bags for a 5x8 slab?
About 23 bags at 4 inches thick.
How many 60 lb bags for a 5x8 slab?
About 30 bags at 4 inches thick.
How many bags for a 5x8 slab 6 inches thick?
About 34 bags of 80 lb mix or 45 of 60 lb.
How much does an 80 lb bag of concrete yield?
About 0.6 cubic feet of mixed concrete.
When is bagged concrete practical?
Usually for jobs under about a cubic yard. Beyond that, mixing dozens of bags by hand gets slow and batches may not blend well.
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 5x5 Slab?
- How Many Bags of Concrete for a 5x6 Slab?
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