How Many Concrete Bags Do I Need?

Keep all dimensions in compatible units

For US dimensions, convert slab depth from inches to feet before multiplying. A 4 inch slab is 0.333 ft deep.

For metric work, meters × meters × meters produces cubic meters. A depth entered in centimeters must be divided by 100.

Bag weight is not the same as mixed yield

Two mixes with similar bag weights can state different finished yields. Use the manufacturer's volume yield instead of estimating from weight.

For a 10×10 ft slab at 4 inches, finished volume is about 33.3 ft³. Adding 8% produces a 36 ft³ order target.

• Divide by 0.60 ft³ yield: 60 bags
• Divide by 0.45 ft³ yield: 80 bags
• Round fractional bags upward

Know when ready-mix is more practical

Mixing dozens of bags requires time, water control and continuous placement. Larger or structural pours may be better suited to delivered concrete.

Quantity is only one decision. Mix specification, reinforcement, subgrade and slab design should follow the project requirements.