Question 1

How many bags of concrete for a 10x10 slab?

Accepted Answer

A 10x10 ft slab at 4 inches thick requires about 1.23 cubic yards of concrete. Using 80 lb bags (roughly 0.60 cubic feet each), that is approximately 61 bags. At that size, ready-mix is usually cheaper and faster. Always add 10% for waste, spills, and uneven subgrade.

Question 2

How thick should a driveway be?

Accepted Answer

A residential driveway should be at least 4 inches thick for passenger vehicles. For heavier loads such as trucks and RVs, use 5 to 6 inches. In cold climates a 4 to 6 inch compacted gravel base prevents frost heave. ACI 330 recommends 4 inches minimum with a 4,000 PSI mix.

Question 3

How do I calculate cubic yards of concrete?

Accepted Answer

Multiply Length (ft) by Width (ft) by Thickness (in) divided by 12, then divide by 27. Example: a 20x20 slab at 4 inches is 20 x 20 x (4/12) = 133.33 cubic feet, divided by 27 = 4.94 cubic yards. Add 10% for waste.

Question 4

How much does a cubic yard of concrete cost?

Accepted Answer

Ready-mix typically runs $130 to $200 per cubic yard depending on region, PSI spec, and supplier. Higher-strength mixes (4,000 to 5,000 PSI) cost $10 to $30 more per yard. Short-load fees may apply under 5 yards.

Question 5

How thick should a concrete slab be?

Accepted Answer

Residential slabs such as patios, garage floors, and sidewalks are typically 4 inches. Driveways are 4 to 6 inches. Industrial floors are 6 inches or more. Thickened edges (8 to 12 inches deep) are recommended around exterior slab perimeters.

Question 6

What is the difference between cubic feet and cubic yards?

Accepted Answer

There are 27 cubic feet in one cubic yard (3 by 3 by 3 ft). In the US, concrete is sold by the cubic yard, so the calculator result is the number to give your supplier.

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