40×40 Concrete Slab Cost
A 40×40-foot slab covers 1,600 square feet. At 4 inches thick, this calculator estimates $8,800–$19,200 installed, using its January 2026 price assumptions. Compare that planning range with ready-mix alone, then adjust thickness and region below.
Concrete (4", waste in)
21.73 yd³
978 × 80 lb bags
Materials (ready-mix)
$2,716 – $4,128
delivered, 4" slab
Installed by a pro
$8,800 – $19,200
4" slab, national average
40×40 slab cost calculator
Adjust thickness, waste or region — the cost updates live.
Waste & region
Order extra for spillage & uneven subgrade. 10% is typical.
Installed cost estimate
$8,800 – $19,200
1,600 sq ft · 21.73 yd³ concrete
Bags of concrete needed (rounded up)
978
80 lb
1,304
60 lb
1,565
50 lb
1,956
40 lb
- Ready-mix (delivered)
- $2,716 – $4,128
- Bagged mix (80 lb, DIY)
- $5,379 – $8,802
- Installed by a pro
- $8,800 – $19,200
Estimate only — not a quote. Bag counts are rounded up and include a 10% waste allowance.
40×40 slab cost by thickness
| Thickness | Concrete | 80 lb bags | Ready-mix | Installed |
|---|---|---|---|---|
| 4" | 21.73 yd³ | 978 | $2,716 – $4,128 | $8,800 – $19,200 |
| 5" | 27.16 yd³ | 1,223 | $3,395 – $5,161 | $10,000 – $20,400 |
| 6" | 32.59 yd³ | 1,467 | $4,074 – $6,193 | $11,200 – $21,600 |
Includes a 10% waste allowance; bag counts rounded up. National US averages, January 2026.
You'll also need
Sized for this exact slab — tap any item to open its calculator with your measurements already filled in.
40×40 concrete slab: what to expect
A 40×40-foot slab has a net concrete volume of 19.75 yd³ at 4 inches thick. A 10% ordering allowance increases this to 21.73 yd³, or 978 bags at an assumed yield of 0.6 ft³ per 80 lb bag. At 6 inches the volume with the same allowance is 32.59 yd³. Thickness and reinforcement must suit the loads, soil and local requirements; these quantities are planning examples, not a structural design.
Budget around $8,800 – $19,200 to have a 4" slab this size poured and finished by a contractor, or roughly $2,716 – $4,128 in ready-mix if you're doing the labor yourself. On top of the concrete you'll need about 22.72 yd³ of gravel base and 108 sticks of rebar.
At 1,600 sq ft this pour will likely need more than one ready-mix truckload, plus enough crew to screed and finish it before it sets — factor truck access into your planning.
This footprint is a common size for a shop / warehouse pad — see the project guides for the full base-to-cost build order if that's what you're planning.
Installed price or concrete only: compare the same scope
The 4-inch installed range on this page corresponds to $5.50–$12 per square foot. The ready-mix range prices the concrete volume separately. These are alternative estimates: do not add the ready-mix amount to an installed quote that already includes concrete.
- Ask what is included: excavation, disposal, compacted base, forms, reinforcement, concrete, placement, finishing and joints.
- Ask about extras: pumping or difficult access, permits, testing, demolition and special finishes. Have the contractor state any exclusions.
- Match the design: compare the same thickness, mix, reinforcement and edge or footing details. A building foundation may need work beyond a flat slab.
The material cards use assumed layers and spacing. Confirm which are needed and already included in your quote before adding their costs. The gravel figure includes an ordering allowance; it is not the compacted volume in place.
How much concrete should you order?
For the default 4-inch example: 40 × 40 × (4 ÷ 12) ÷ 27 = 19.753 cubic yards before waste. Multiply by 1.10 to get 21.728 cubic yards, displayed as 21.73. Confirm the supplier’s order increments and delivery arrangements; a rounded calculator result is not an order specification.
Changing the waste factor changes ordered concrete and bag quantities. It does not increase the slab’s floor area. Use the thickness table to compare the 4-, 5- and 6-inch scenarios with the same 40×40 footprint.
Compare nearby sizes
Planning something bigger or smaller? Jump straight to the cost for a nearby size.
Volumes use standard bag yields and a 10% waste allowance; costs are national US averages that vary by region, mix and finish. See our methodology for exactly how each figure is worked out, or check the reference sources: