Hardscape
Concrete Calculator
Enter your slab size and thickness. Four inches is standard for a patio or walkway; six for a driveway or anything bearing vehicle weight.
At a glance
- Usual depth
- 4 in
- Answer in
- cubic yards
100 sq ft at 4 in deep needs:
1.23 cubic yardsof concrete
- ≈ 56 bags (80 lb)
- ≈ 75 bags (60 lb)
An 80 lb bag yields about 0.60 cu ft; a 60 lb bag about 0.45 cu ft. Past roughly half a cubic yard, ready-mix delivery is usually cheaper and easier than bags.
Hardscape
The base matters more than the surface
Most failed patios and driveways are base failures, not material failures. Get the compacted depth right for Triangle clay and the top layer will outlast the person who laid it.
How this is worked out
No hidden fudge factor. This is the whole calculation.
- Length times width gives the area in square feet.
- Area times the depth in feet, which is your inches divided by 12, gives cubic feet.
- Cubic feet divided by 27 gives cubic yards, because a yard is 3 feet cubed.
- Bag counts assume about 45 eighty-pound bags or 60 sixty-pound bags to the cubic yard.
Common questions
- How much concrete do I need?
- Multiply your area's length by its width for square feet, then by the depth in feet (inches ÷ 12), and divide by 27 for cubic yards. This calculator does it for you. Enter length, width, and depth.
- How many bags of concrete are in a cubic yard?
- About 45 eighty-pound bags, or 60 sixty-pound bags, make a cubic yard. Past roughly half a yard, ready-mix delivery is usually cheaper.