30x30 Concrete Slab Cost Calculator - 2026 Quote Check
Estimate 30x30 concrete slab cost with cubic yards, ready-mix pricing, thickness, base prep, reinforcement, access, finish, and bid scope.
A 30x30 concrete slab is 900 sq ft, so small changes in thickness, base prep, reinforcement, delivery, and access can move the quote quickly. This size often shows up for garages, shops, barns, equipment pads, and large flatwork areas.
Use the Concrete Garage Slab Calculator Guide when the slab is for a garage. Use the Concrete Slab Calculator for the exact volume and the Concrete Quote Reviewer when comparing bids.
Quick answer
A 30x30 slab is 900 sq ft. At 4 in thick, it needs about 11.11 yd3 before waste or 12.22 yd3 with 10% waste. At $165 per yd3 and a $125 delivery placeholder, the ready-mix material check is about $2,141.30 before tax, pump, base, steel, labor, finish, and local fees.
For garage, shop, or load-bearing use, thickness, reinforcement, vapor barrier, subbase, compaction, drainage, and permits should be confirmed with a qualified local professional.
30x30 slab quantity table
These examples use a 30 ft by 30 ft slab and 10% waste.
| Thickness | Cubic yards before waste | Cubic yards with 10% waste | Ready-mix at $165/yd3 + $125 |
|---|---|---|---|
| 4 in | 11.11 | 12.22 | $2,141.30 |
| 5 in | 13.89 | 15.28 | $2,646.20 |
| 6 in | 16.67 | 18.33 | $3,149.45 |
| 8 in | 22.22 | 24.44 | $4,157.60 |
This is a material check only. A 30x30 slab is usually beyond a bagged-concrete workflow. Ready-mix delivery, pump access, finishing crew size, and saw-cut timing should be planned before pour day.
Installed quote items for a 30x30 slab
| Scope item | Why it matters |
|---|---|
| Subgrade and excavation | Soft spots, cut/fill, and compaction can change price. |
| Gravel base | Depth and compaction affect performance and drainage. |
| Vapor barrier | Often relevant for garages, shops, and interior slabs. |
| Reinforcement | Rebar, mesh, fiber, dowels, or none should be specified. |
| Thickened edge | A mono slab or edge beam changes concrete volume. |
| Placement method | Chute, pump, buggy, or direct access affects labor and fees. |
| Finish and joints | Large slabs need finish timing and joint layout in writing. |
For vapor barrier scope, see Concrete Vapor Barrier Cost. For thickened edges, see Concrete Thickened Edge Slab Cost.
Why 30x30 quotes vary
Two bids for a 30x30 slab can both say "900 sq ft" and still describe different jobs. One may include excavation, gravel, rebar, vapor barrier, saw cuts, pump, and cleanup. Another may include only forming and pouring over a prepared base.
Normalize every bid before comparing:
installed cost per sq ft = full quote / 900
material cost per sq ft = concrete material check / 900
If a bid is much lower, check whether base prep, steel, access, saw cuts, permits, cleanup, or warranty are excluded. Contractors can use the Concrete Proposal Kit to show those lines clearly.
FAQ
How many yards of concrete are needed for a 30x30 slab?
At 4 in thick, a 30x30 slab needs about 11.11 yd3 before waste or 12.22 yd3 with 10% waste. A 6 in slab needs about 18.33 yd3 with 10% waste.
How much does ready-mix cost for a 30x30 slab?
Using $165 per yd3 and a $125 delivery placeholder, a 4 in 30x30 slab has a material check around $2,141.30 before tax and local fees.
Is a 30x30 slab practical with bags?
Usually no. The bag count is too high for most DIY workflows. Ready-mix with a planned crew and access method is usually more realistic.
What should a 30x30 slab quote include?
It should show thickness, base prep, forms, reinforcement, vapor barrier if needed, access, finish, joints, curing, cleanup, exclusions, and warranty.
Is this engineering advice?
No. It is a cost and quote planning guide. Confirm slab design, loads, soil, code, and permit requirements with a qualified local professional.
Next step
Use the Concrete Slab Calculator, then compare the full bid in the Concrete Quote Reviewer before approving the work.
Quote planning next step
Turn this guide into a concrete buying check
Run the matching calculator, then compare ready-mix, bagged concrete, delivery fees, access needs, and quote gaps before you buy materials or approve a contractor number.