Concrete Calculator – How Much Concrete Do I Need? | CalcLoft
Find out exactly how much concrete you need in cubic feet, cubic yards and bags — for slabs, patios and footings.
How much concrete do I need?
Concrete is ordered by volume. For a slab, multiply length × width × depth. Convert depth to feet first (4 inches = 0.333 ft). For example, a 10 × 10 ft patio at 4 inches deep is 10 × 10 × 0.333 = 33.3 cubic feet = about 1.23 cubic yards.
Bags vs. ready-mix
For small jobs (under 1 cubic yard), bags are easiest. A 60 lb bag yields about 0.45 cu ft. For larger projects, ready-mix concrete delivered by truck is cheaper per yard — but you usually pay for a minimum of 1–2 cubic yards.
Should I add extra concrete?
Yes — add 5–10% for uneven ground, spillage and form variations. The calculator adds nothing by default, so round up when ordering.
Concrete calculator FAQ
How many 60 lb bags are in a cubic yard?
A cubic yard is 27 cu ft. A 60 lb bag makes about 0.45 cu ft, so you need roughly 60 bags per cubic yard (27 ÷ 0.45).
Can I mix concrete by hand?
For small areas yes, but for anything over 1/2 cubic yard, rent a mixer or order ready-mix — hand mixing is exhausting and inconsistent.
Is 4 inches of concrete enough?
4 inches is fine for walkways and light use. Driveways should be 5–6 inches, and anything supporting vehicles regularly should be 6 inches or more.
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