20x40 Concrete Slab Cost
A 20x40 concrete slab costs $6,562 to $10,936 installed with rebar, or $8.20 – $13.67 per square foot. Change the thickness for an RV or enter a ZIP for a local price in the calculator below.
LIKELY INSTALLED PRICE
$8,749
Our installed range for this 20×40 ft, 4-inch slab: $6,562 – $10,936 ($8.20 – $13.67 per sq ft)
In plain terms: that's about the size of a three-car garage floor, and roughly 45% of the price is the crew's labor.
- DIY materials
- $4,628
- Concrete
- 9.88 yd³
- Bagged mix
- 489 80-lb bags
- Delivery
- 2 trucks
An estimate, not a bid. A contractor's price depends on your site, access and timing.
What changes the price
Where the money goes
- Materials$3,984
- Labor$3,306
- Overhead and profit (20%)$1,458
All 8 line items
| Item | Qty | Material | Labor | Total |
|---|---|---|---|---|
| Site setup, layout and cleanup | 1 job | $100 | $56 | $156 |
| Excavate and grade subgrade | 800 sqft | $0 | $888 | $888 |
| Forms, stakes and form release | 120 lf | $144 | $266 | $410 |
| Compacted crushed-stone base | 13.83 ton | $622 | $256 | $878 |
| #4 rebar, tied on chairs | 1126.67 lf | $1,124 | $500 | $1,624 |
| Ready-mix concrete, 3,500 psi, delivered | 10.37 yd3 | $1,804 | $230 | $2,034 |
| Place, screed and broom finish | 800 sqft | $40 | $1,036 | $1,076 |
| Sawn control joints | 100 lf | $150 | $74 | $224 |
| Subtotal × overhead and profit (20%) = midpoint | $8,749 | |||
National prices until you enter a ZIP.
Got a quote? Check it
Compare a contractor's price with the range for these inputs.
What next
Get two or three quotes and compare them with $6,562 – $10,936. DIY: 489 bags or 10.37 yd³ of ready-mix.
Tell me when local quotes openQuote matching is not live yet; we may earn a fee later.
Turn this price into an estimate for your customer →Cost by thickness for 20x40 (800 sq ft)
4 in · patios, sheds
$6,562 – $10,936
9.88 yd³ · 489 bags · about $8,749
5 in · garages, driveways
$7,019 – $11,699
12.35 yd³ · 612 bags · about $9,359
6 in · shops, RV pads
$7,437 – $12,395
14.81 yd³ · 734 bags · about $9,916
- Typical use
- Mostly RV and boat pads, sometimes a long carport.
- Thickness
- 4 inches with rebar for cars and light trailers; 5 to 6 inches for motorhomes.
- Planning note
- Slope the slab along its length so water drains off the end, not toward the building.
20x40 slab for an RV or boat
Forty feet fits most travel trailers and boats with room to walk around them. Heavier RVs usually call for more than the 4 inches priced here.
What drives the 20x40 cost
The long sides mean 120 linear ft of forms and more edge finishing. Concrete, 1,127 linear ft of rebar and 13.8 tons of gravel are the big material lines.
Getting concrete to the far end
At 10.37 yd³ on 2 trucks, the chute won't reach the back of a 40-foot slab from one spot. Budget for a pump or clear a path for the truck.
Estimate or quote?
Treat this as an estimate for planning and bid checking. A contractor's quote will reflect your access and soil and is the number to sign.
DIY vs pro for this 20x40 pour
Materials alone come to $4,628, about 53% of the $8,749 midpoint contractor price. The difference is $4,120 of labor, equipment, delivery and contractor overhead across 8 line items. At 10.37 yd³ with waste the pour fills 2 mixer trucks, so ready-mix is the practical route even for a DIY pour.
Other popular slab sizes
- 20x20 concrete slab cost$2,874 – $4,789400 sq ft · 4.94 yd³ at 4 in
- 24x24 concrete slab cost$4,848 – $8,080576 sq ft · 7.11 yd³ at 4 in
- 20x30 concrete slab cost$4,983 – $8,306600 sq ft · 7.41 yd³ at 4 in
- 30x30 concrete slab cost$7,324 – $12,206900 sq ft · 11.11 yd³ at 4 in
- 30x40 concrete slab cost$9,664 – $16,1061,200 sq ft · 14.81 yd³ at 4 in
- 30x50 concrete slab cost$12,004 – $20,0061,500 sq ft · 18.52 yd³ at 4 in
Compare with the next sizes
Garage concrete slab cost calculatorAll slab sizes and the full calculator
Frequently asked questions
How thick should an RV pad be?
Builders commonly pour 5 to 6 inches with rebar for motorhomes. Change the thickness in the calculator to price it.
How much concrete is a 20x40 slab?
9.88 yd³ at 4 inches. Ordered with the usual extra, it's 10.37 yd³.
Do I need a permit for an RV pad?
Many towns require one for large flatwork or anything within setback lines. Some HOAs also limit RV parking.
Is gravel cheaper than a concrete RV pad?
Gravel costs less up front but ruts and needs topping up. Concrete costs more once and stays flat.
For contractors
Quoting concrete for customers?
The free estimating app opens with a sample concrete job priced the same way. Read more about concrete estimating software.