Concrete Calculator › 30×30 slab

Concrete for a 30×30 Slab at 4 inches

A 30×30 slab (900 sq ft) at 4 inches needs about 11.11 cubic yards of concrete — roughly $1,667. See the full breakdown.

You need
11.11 cu yd
Estimated material cost $1,667
Area
900 sq ft
Volume
300.0 cu ft
80-lb bags
500
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Adjust for your project

You need
11.11 cu yd
Estimated material cost $1,667
Area
900 sq ft
Volume
300.0 cu ft
80-lb bags
500

Material shopping list

  • Order about 11.11 cubic yards of concrete.
  • Budget about $1,667 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 30×30 slab

How many bags of concrete do I need for a 30×30 slab at 4 inches?
You need 300.0 cubic feet: about 500 80-lb bags, 667 60-lb bags, or 1000 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 30×30 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.