Concrete Calculator › 20×24 slab
Concrete for a 20×24 Slab at 4 inches
A 20×24 slab (480 sq ft) at 4 inches needs about 5.93 cubic yards of concrete — roughly $889. See the full breakdown.
You need
5.93 cu yd
Estimated material cost $889
Area
480 sq ft
Volume
160.0 cu ft
80-lb bags
267
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Adjust for your project
You need
5.93 cu yd
Estimated material cost $889
Area
480 sq ft
Volume
160.0 cu ft
80-lb bags
267
Material shopping list
- Order about 5.93 cubic yards of concrete.
- Budget about $889 before delivery, taxes, and labor.
- Add 5–10% waste for uneven subgrade, cuts, settling, or spillage.
Formula & assumptions
Area = length x width. Volume = area x depth / 12. Cubic yards = cubic feet / 27. Cost = quantity x local unit price.
- Default depth: 4 inches
- Default price: $150 per cuyd
- 80-lb bags yield: 0.6 cu ft each
These assumptions make the estimate easy for search engines and AI answer tools to verify. Replace the default price with your supplier quote for a local estimate.
Common questions about a 20×24 slab
- How many bags of concrete do I need for a 20×24 slab at 4 inches?
- You need 160.0 cubic feet: about 267 80-lb bags, 356 60-lb bags, or 534 40-lb bags. At that count, ready-mix delivery is cheaper, faster, and gives a consistent mix — bags make sense only if truck access is impossible.
- How much weight can a 4-inch concrete slab hold?
- A properly poured 4-inch slab over compacted base handles foot traffic, patios, sheds, and passenger cars without trouble. For pickups, RVs, or point loads like jack stands and lifts, step up to 5–6 inches with rebar.
- Should I pour thicker than 4 inches?
- Only if vehicles will use it. Thickening a 20×24 slab from 4 to 6 inches adds 50% more concrete — worth it for a driveway, wasted on a patio. Spend the difference on base compaction instead; slabs fail from bad subgrade far more often than from thin concrete.
- Do I need rebar or wire mesh?
- For patios and walkways, fiber-reinforced mix or wire mesh controls cracking fine. For driveways and anything carrying vehicles, use #3 or #4 rebar on an 18–24 inch grid, set on chairs at mid-slab — mesh stomped to the bottom of the pour does nothing.
Based on $150 per cuyd national average. Enter your local price for an exact quote. Estimate only.