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Home & Garden — Concrete
Concrete Calculator
Enter your slab length, width and thickness to get the cubic yards and the number of bags to buy.
number of slabs
Concrete needed
—
Cubic yards to order.
| Cubic feet | — |
|---|---|
| 60 lb bags | — |
| 80 lb bags | — |
| +10% waste (yd³) | — |
Show our math
Enter your figures above to see the step-by-step working.
Estimate — order ~10% extra to be safeEverything computed client-side — nothing leaves this page
How the Concrete Calculator Works
Concrete is ordered by volume, usually in cubic yards. To find how much you need, multiply the length, width and thickness of your slab — converting the thickness from inches to feet first — to get cubic feet, then divide by 27 to convert to cubic yards. This calculator does that and also tells you how many 60 lb or 80 lb bags of pre-mix it would take.
Because some concrete is always lost to spillage, uneven subgrade and over-excavation, it is wise to order about 10% extra; the calculator shows that figure too. For a ready-mix truck, round up — running short mid-pour is far worse than a little waste.
cubic yards = (length × width × thicknessft) ÷ 27
Frequently Asked Questions
How many bags of concrete are in a cubic yard?
A cubic yard is 27 cubic feet. An 80 lb bag makes about 0.60 cubic feet, so it takes roughly 45 of them per cubic yard; a 60 lb bag makes about 0.45 cubic feet, or about 60 bags per yard.
Should I order extra concrete?
Yes — about 5–10% extra is standard to cover spillage, uneven ground and waste. The calculator shows a 10% cushion; for a truck order, round up rather than risk running short.
How thick should a concrete slab be?
Four inches is typical for patios, walkways and sheds; five to six inches for driveways and areas that carry vehicles. Enter your thickness in inches and the calculator converts it for you.
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