To calculate how many bags of concrete you need for an 2×4 slab, you’ll first need to determine the thickness of the slab you want. Standard concrete slabs are typically 4 inches thick, but you may want a different thickness depending on your project.

Concrete is a blended mix of Portland cement, sand, aggregate, water with approve ingredient. Cement is acts as binder or adhesive materials to bind the components of concrete all together to create workable paste. Sand acts as filler material that fills the voids and gap between components of concrete and remove the air. Aggregate, stone, or gravel used to strengthen the concrete strength.

To determine how many bags of premixed concrete you will need, divide the total cubic yards needed by the yield. Use the following yields per each bag size: A 40 pound bag yields 0.011 cubic yards, 60 pound bag yields 0.017 cubic yards, 50 pound bag yields 0.0138 cubic yards and 80 pound bag yields 0.022 cubic yards.

If you measure their yields in cubic feet, then yields per each bag size are following: A 40 pound bag yields 0.30 cubic feet, 60 pound bag yields 0.45 cubic feet, 50 pound bag yields 0.375 cubic feet and 80 pound bag yields 0.60 cubic feet.

To figure the amount of yards of concrete you will need, take the all measurements Length in feet, width in feet and thickness in inches. Convert thickness in feet. Multiply its length, width and thickness to get cubic footage. Multiply the total cubic footage by 0.037 to get total yards of concrete needed.

**How many bags of concrete do i need for a 2×4 slab**

The amount of concrete you need for a 2×4 slab depends on how thick it will be. So, for a 4-inch slab you’ll need 0.105 cubic yards, or 2.83 cubic feet (5 80lb bags), a 3-inch slab requires 0.074 cubic yards, or 2 cubic feet (4 80lb bags), but a 2-inch slab requires 0.049 cubic yards, or 1.33 cubic feet (3 80lb bags).

**How many bags of concrete do i need for a 2×4 slab at 2 inches thick**

At 2 inches thick, for a 2×4 slab you would need approximately either 3 80-Pound, 3 60-pound, or 5 40-pound bags of premixed concrete. If you measure in yards, 0.049 cubic yards (or 1.33 cubic feet) of concrete will be required.

**Let’s do calculation and proceeds following steps:**

- Convert 2″ thickness in feet = 2/12 = 0.166′
- Volume of concrete in cubic feet = 2 × 4 × 0.166 = 1.33 cubic feet
- Volume of concrete in yards = 1.33 × 0.037 = 0.049 cubic yards.
- Estimate No. of 80lb bags = 1.33/0.60 = 3 bags
- Estimate No. of 60lb bags = 1.33/0.45 = 3 bags
- Estimate No. of 40lb bags = 1.33/0.30 = 5 bags.

**How many bags of concrete do i need for a 2×4 slab at 3 inches thick**

At 3 inches thick, for a 2×4 slab you would need approximately either 4 80-Pound, 5 60-pound, or 7 40-pound bags of premixed concrete. If you measure in yards, 0.074 cubic yards (or 2 cubic feet) of concrete will be required.

**Let’s do calculation and proceeds following steps:**

- Convert 3″ thickness in feet = 3/12 = 0.25′
- Volume of concrete in cubic feet = 2 × 4 × 0.25 = 2 cubic feet
- Volume of concrete in yards = 2 × 0.037 = 0.074 cubic yards.
- Estimate No. of 80lb bags = 2/0.60 = 4 bags
- Estimate No. of 60lb bags = 2/0.45 = 5 bags
- Estimate No. of 40lb bags = 2/0.30 = 7 bags.

**How many bags of concrete do i need for a 2×4 slab at 4 inches thick**

At 4 inches thick, for a 2×4 slab you would need approximately either 5 80-Pound, 7 60-pound, or 10 40-pound bags of premixed concrete. If you measure in yards, 0.105 cubic yards (or 2.83 cubic feet) of concrete will be required.

**Let’s do calculation and proceeds following steps:**

- Convert 4″ thickness in feet = 4/12 = 0.333′
- Volume of concrete in cubic feet = 2 × 4 × 0.333 = 2.83 cubic feet
- Volume of concrete in yards = 2.83 × 0.037 = 0.105 cubic yards.
- Estimate No. of 80lb bags = 2.83/0.60 = 5 bags
- Estimate No. of 60lb bags = 2.83/0.45 = 7 bags
- Estimate No. of 40lb bags = 2.83/0.30 = 10 bags.

**Here’s are table for how much concrete do i need for a 2×4 slab:**

SL.no. |
Thickness |
Amount in Cubic feet |
No. of 80 lb bags |
No. of 60 lb bags |
No. of 50 lb bags |
No. of 40 lb bags |

1 | 2″ | 1.33 | 0.049 | 3 | 3 | 5 |

2 | 3″ | 2 | 0.074 | 4 | 5 | 7 |

3 | 4″ | 2.83 | 0.105 | 5 | 7 | 10 |

**Cost estimate for a 2×4 slab**

The cost of a 2×4 slab can vary based on factors like location, materials used, and labor costs. On average, you might expect to pay between $4 and $8 per square foot for a basic concrete slab. Therefore, a 2’x4′ slab could cost roughly between $32 to $64, excluding additional expenses like site preparation or finishing touches.

**Conclusions:**If you have a 2×4 slab with 4″ thick, you’ll need approximately either 5 80lb, or 7- 60lb (0.105 yards, or 2.83 cubic feet) bags of premixed concrete which will cost an average of $32 including labour.