Cost of a 12 x 20 Concrete Slab
A 12 x 20 concrete slab costs $1,922 to $3,203 installed at 4 inches ($8.01 – $13.35 per square foot). Edit the size, finish or ZIP in the calculator to rework the figure.
LIKELY INSTALLED PRICE
$2,563
Our installed range for this 12×20 ft, 4-inch slab: $1,922 – $3,203 ($8.01 – $13.35 per sq ft)
In plain terms: that's about the size of a one-car garage or a roomy patio, and roughly 47% of the price is the crew's labor.
- DIY materials
- $1,175
- Concrete
- 2.96 yd³
- Bagged mix
- 147 80-lb bags
- Delivery
- 1 truck, short load
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$1,138
- Labor$998
- Overhead and profit (20%)$427
All 9 line items
| Item | Qty | Material | Labor | Total |
|---|---|---|---|---|
| Site setup, layout and cleanup | 1 job | $100 | $56 | $156 |
| Excavate and grade subgrade | 240 sqft | $0 | $266 | $266 |
| Forms, stakes and form release | 64 lf | $77 | $142 | $219 |
| Compacted crushed-stone base | 4.15 ton | $187 | $77 | $263 |
| 6x6 W1.4 welded wire mesh | 240 sqft | $88 | $53 | $141 |
| Ready-mix concrete, 3,500 psi, delivered | 3.11 yd3 | $541 | $69 | $610 |
| Short-load delivery fee | 1 job | $85 | $0 | $85 |
| Place, screed and broom finish | 240 sqft | $12 | $311 | $323 |
| Sawn control joints | 32 lf | $48 | $24 | $72 |
| Subtotal × overhead and profit (20%) = midpoint | $2,563 | |||
National prices until you enter a ZIP.
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Compare a contractor's price with the range for these inputs.
What next
Get two or three quotes and compare them with $1,922 – $3,203. DIY: 147 bags or 3.11 yd³ of ready-mix.
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Turn this price into an estimate for your customer →Cost by thickness for 12x20 (240 sq ft)
4 in · patios, sheds
$1,922 – $3,203
2.96 yd³ · 147 bags · about $2,563
5 in · garages, driveways
$2,019 – $3,365
3.70 yd³ · 184 bags · about $2,692
6 in · shops, RV pads
$2,080 – $3,466
4.44 yd³ · 220 bags · about $2,773
- Typical use
- Most often a large shed or a garden workshop.
- Thickness
- 4 inches with mesh for storage; add thickness under any spot where a heavy machine will sit.
- Planning note
- Mark where the doors go so the finisher can keep the threshold flat and the slab edge square there.
12 x 20 slab for a large shed or workshop
A 240-square-foot base takes a garden workshop, a lean-to carport or a two-door storage building. If you'll run a table saw or park a mower, add an outlet conduit before the pour.
How the 12 x 20 cost adds up
Concrete, 4.1 tons of gravel, 240 sq ft of wire mesh and forming along 64 linear ft are the main materials. The rest is labor and contractor overhead, listed line by line above.
Ordering concrete for 240 sq ft
Order 3.11 yd³ with waste, one delivery on 1 truck. Mixing 147 bags by hand is possible, but a truck is usually cheaper at this size.
Why a written bid may differ
This is a planning estimate, not a contractor quote. A bid can be higher for a sloped yard, poor truck access or old concrete to remove.
DIY vs pro for this 12x20 pour
Materials alone come to $1,175, about 46% of the $2,563 midpoint contractor price. The difference is $1,388 of labor, equipment, delivery and contractor overhead across 9 line items. At 3.11 yd³ the pour is under the short-load threshold, so bagged mix or a shared truck avoids a delivery fee.
Other popular slab sizes
- 10x12 concrete slab cost$1,094 – $1,823120 sq ft · 1.48 yd³ at 4 in
- 12x12 concrete slab cost$1,279 – $2,132144 sq ft · 1.78 yd³ at 4 in
- 10x20 concrete slab cost$1,625 – $2,708200 sq ft · 2.47 yd³ at 4 in
- 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
Compare with the next sizes
Shed concrete slab cost calculatorAll slab sizes and the full calculator
Frequently asked questions
Is 12x20 too big to pour with bags?
It's possible but hard: 147 bags means a mixer and a crew all day. Most people order ready-mix at this size.
Does a 12x20 shed slab need a building permit?
Buildings this size are over the exemption limit in many towns. Ask before pouring, because an inspector may want to see the forms and base.
How much gravel goes under a 12x20 slab?
The estimate uses 4.1 tons for a compacted base. Change the base depth in the calculator to see the effect.
Can a 12x20 slab be a garage floor?
It fits one compact car, but a garage floor is usually thicker and rebar-reinforced. Price it on the garage calculator instead.
For contractors
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