Concrete calculator
Slab volume in cubic yards, ordered in quarter-yard steps the way the plant sells it.
Concrete
Slab volume in cubic yards, ordered in quarter-yard steps the way the plant sells it.
Short-load fees apply under one yard. Below half a yard, bags are cheaper than a truck.
$578
3.50 cubic yards of 3000 psi ready-mix at $165.00 / cu yd
Free. No signup. The quantities carry over as line items.
How this concrete calculator works
Volume in cubic yards, ordered the way the plant actually sells it — in quarter-yard steps, with a short-load fee under a yard.
The formula
cu yd = length × width × (thickness ÷ 12) ÷ 27, ordered up to the next quarter yard
Assumptions and defaults
| Default waste | 10% |
| Order step | quarter yard |
| 80 lb bag yield | 0.60 cu ft |
| 60 lb bag yield | 0.45 cu ft |
| Bags per yard | 45 at 80 lb |
Pro tips
Order ten per cent over. Subgrade is never as flat as you think, and running half a yard short on a pour is a bad afternoon that ends in a cold joint.
Under half a yard, bags beat a truck. Over a yard, a truck beats bags on both money and your back.
Tell the plant your slump and mix before you tell them the yardage. Short loads book by truck time, not volume.
Common questions
How much concrete do I need for a 10 × 10 slab?
At 4 inches thick that is 33.3 cubic feet, or 1.23 cubic yards. Add ten per cent for subgrade variation and order 1.5 yards.
How many 80 lb bags in a yard of concrete?
45. An 80 lb bag yields 0.60 cubic feet and a yard is 27 cubic feet.
How thick should a concrete slab be?
Four inches for patios, walks and garage floors. Five to six where vehicles heavier than a car will sit, with rebar rather than mesh.
What is a short-load fee?
Most plants charge extra under about a yard, because they are sending a truck either way. It can be $60–150, which is why bags win on small pours.