How Many Bags of Concrete for a 4x5 Slab?
Small pads like a 4x5 suit bagged mix. How many bags of concrete for a 4x5 slab at a standard 4-inch depth: 12 × 80 lb, or 15 × 60 lb, since each bag yields only about 0.6 or 0.45 cubic feet.
Concrete calculator →How the bag count is figured
- Area: 4 × 5 = 20 sq ft.
- Volume at 4 in: 20 × 0.333 = 6.67 cu ft.
- 80 lb bags: 6.67 ÷ 0.60 = 11.1, round up to 12.
- 60 lb bags: 6.67 ÷ 0.45 = 14.8, round up to 15.
Check the yield printed on your brand’s bag, since it varies a little. The concrete calculator handles other shapes.
Related: How Much Sand for a 4x5 Sandbox?
Bags by thickness for a 4x5 slab
| Thickness | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|
| 3 in | 5.00 | 9 | 12 | 17 |
| 4 in | 6.67 | 12 | 15 | 23 |
| 5 in | 8.33 | 14 | 19 | 28 |
| 6 in | 10.00 | 17 | 23 | 34 |
Bags or a truck?
At 0.25 cubic yards, this pad is well under the point where a ready-mix truck starts to make sense. Many plants charge a small-load fee on tiny orders, so bags are often cheaper here, and a rented mixer makes 12 bags manageable for two people.
Related: How Many Bags of Concrete for a 10x10 Slab?
Prep for a small slab
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. Mix to a stiff, oatmeal-like consistency; extra water makes it easier to place but weaker.
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 4x5 slab?
About 12 bags at 4 inches thick.
How many 60 lb bags for a 4x5 slab?
About 15 bags at 4 inches thick.
How many bags for a 4x5 slab 6 inches thick?
About 17 bags of 80 lb mix or 23 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 3x5 Slab?
- How Many Bags of Concrete for a 4x4 Slab?
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