Concrete slab calculator
Pouring a patio, shed base, or walkway? This concrete slab calculator turns your slab's length, width, and thickness into cubic yards — plus how many 80 lb bags you need for smaller pours.
Concrete slab calculator FAQ
How do you calculate concrete for a slab?
Multiply length × width × (thickness ÷ 12) to get cubic feet, then divide by 27 for cubic yards. A 10×10 ft slab at 4 inches thick needs about 1.23 cubic yards.
How many 80 lb bags of concrete are in a cubic yard?
An 80 lb bag yields about 0.6 cubic feet, so one cubic yard (27 cubic feet) takes about 45 bags.
Should I order extra concrete?
Yes — most projects add 5–10% for waste and uneven ground. This concrete slab calculator shows a 10%-extra figure.
How thick should a concrete slab be?
4 inches is typical for patios and walkways; driveways and heavy loads usually need 5–6 inches on a compacted base.
Can I mix feet and inches?
Enter length and width in feet and thickness in inches — the calculator converts everything internally.