A 30×40 concrete slab costs $7,200 to $14,400 installed in 2026, with most projects landing near $10,800. That works out to $6.00 – $12.00 per sq ft. Your state changes the number — use the calculator below.
30×40 Concrete Slab cost calculator
Planning estimate only. State pricing applies a construction wage index to the labor share; materials are held at national prices. Get three written quotes before committing.
How much concrete does a 30×40 slab need?
| Thickness | Cubic yards | 80 lb bags | 60 lb bags |
|---|---|---|---|
| 4 inch | 14.81 cu yd | 667 | 889 |
| 5 inch | 18.52 cu yd | 834 | 1112 |
| 6 inch | 22.22 cu yd | 1000 | 1334 |
| 8 inch | 29.63 cu yd | 1334 | 1778 |
Order about 10% extra to cover spillage and uneven subgrade. Once a pour passes roughly 2 cubic yards, ready-mix delivery is almost always cheaper and faster than mixing bags by hand.
30×40 Concrete Slab cost by state
Labor is about 50% of the bill, so the same 30×40 project swings widely between states:
| Cheapest states | Cost | Priciest states | Cost |
|---|---|---|---|
| Mississippi | $9,828 | Hawaii | $12,312 |
| Arkansas | $9,882 | California | $11,988 |
| Alabama | $9,936 | New York | $11,880 |
| South Dakota | $9,990 | Massachusetts | $11,772 |
| West Virginia | $10,044 | Washington | $11,664 |
What fits on a 30×40 concrete slab?
A 30×40 slab is foundation-scale work. Expect engineered drawings, thickened edges or footings, and a pour that needs multiple trucks and a full finishing crew.
Cost by grade and finish
Specification moves the price as much as size does. For a 30×40 project:
| Option | Typical cost | vs standard |
|---|---|---|
| Broom finish (standard) | $10,800 | baseline |
| Smooth trowel | $11,772 | +9% |
| Exposed aggregate | $14,580 | +35% |
| Stamped / decorative | $19,980 | +85% |
How 30×40 compares with nearby sizes
| Size | Installed cost | vs 30×40 |
|---|---|---|
| 10×20 | $1,800 | -83% |
| 12×16 | $1,728 | -84% |
| 12×20 | $2,160 | -80% |
| 12×24 | $2,592 | -76% |
| 14×14 | $1,764 | -84% |
| 16×16 | $2,304 | -79% |
What the price includes
The range above covers materials, labor, standard site preparation, and cleanup for a 30×40 project with normal access. It excludes permits, demolition or removal of existing work, drainage corrections, and upgrades beyond a standard specification.
Materials alone run roughly $5,400 for this size, which is the figure to start from if you are weighing doing it yourself.
What changes the price of a 30×40 concrete slab
Thickness and reinforcement
Moving from 4 to 6 inches raises concrete volume by half. Rebar instead of wire mesh adds roughly $0.75 per square foot but sharply reduces cracking under vehicle loads.
Subgrade condition
Soft, wet, or uneven ground needs excavation and a compacted gravel base. A good base does more for crack prevention than extra slab thickness.
Site access
If a truck cannot reach the pour, concrete has to be pumped or barrowed. Pumping typically adds several hundred dollars to a small job.
Finish
A broom finish is included in base pricing. Stamping, staining, or exposed aggregate can nearly double the installed cost.
Demolition
Removing an existing slab adds material disposal and machine time, often $2 to $6 per square foot before the new pour starts.
How long does a 30×40 concrete slab take?
A 30×40 pour is a multi-day project. Expect several days of excavation, base work, forming, and reinforcement before the pour itself, which may need more than one truck. Full cure runs 28 days, though the slab is usable well before that.
Frequently asked questions
How much does a 30×40 concrete slab cost?
A 30×40 concrete slab costs $7,200 to $14,400 installed in 2026, averaging about $10,800. State labor rates move that figure by 20% or more in either direction.
How much is that per sq ft?
It works out to $6.00 to $12.00 per sq ft. Larger projects usually land slightly lower per sq ft because setup and mobilisation costs spread across more area.
What would it cost to do it myself?
Materials for a 30×40 project run roughly $5,400. The rest is labor, equipment, and disposal. Factor in tool rental and the cost of correcting mistakes before deciding.
Which states are cheapest for this project?
Mississippi and Arkansas are among the lowest at around $9,828, while Hawaii runs closer to $12,312 for the same specification.
How many bags of concrete for a 30×40 slab?
At 4 inches thick, a 30×40 slab needs about 14.81 cubic yards, which is roughly 667 80 lb bags or 889 60 lb bags. Above about 2 cubic yards, ready-mix delivery is usually cheaper.
How long does a 30×40 concrete slab take to complete?
A 30×40 pour is a multi-day project. Expect several days of excavation, base work, forming, and reinforcement before the pour itself, which may need more than one truck. Full cure runs 28 days, though the slab is usable well before that.
What most often pushes a 30×40 project over budget?
Thickness and reinforcement and subgrade condition are the two most common. Moving from 4 to 6 inches raises concrete volume by half. Rebar instead of wire mesh adds roughly $0.75 per square foot but sharply reduces cracking under vehicle loads.
Do I need a permit for a 30×40 concrete slab?
Most jurisdictions require a permit for work of this type and value, and the fee commonly scales with declared project value. Budget a few hundred dollars and confirm with your local building department before work starts, since unpermitted work can surface during a sale or an insurance claim.
Other concrete slab sizes
Open the full concrete slab calculator →