16×20 Concrete Slab Cost
A 16×20 slab covers 320 square feet. Here's the concrete, bags and cost for 2026 — a common size for a one-car garage.
Concrete (4", waste in)
4.35 yd³
196 × 80 lb bags
Materials (ready-mix)
$603 – $1,001
delivered, 4" slab
Installed by a pro
$1,760 – $3,840
4" slab, national average
16×20 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
$1,760 – $3,840
320 sq ft · 4.35 yd³ concrete
Bags of concrete needed (rounded up)
196
80 lb
261
60 lb
313
50 lb
392
40 lb
- Ready-mix (delivered)
- $603 – $1,001
- Bagged mix (80 lb, DIY)
- $1,078 – $1,764
- Installed by a pro
- $1,760 – $3,840
Estimate only — not a quote. Bag counts are rounded up and include a 10% waste allowance.
16×20 slab cost by thickness
| Thickness | Concrete | 80 lb bags | Ready-mix | Installed |
|---|---|---|---|---|
| 4" | 4.35 yd³ | 196 | $603 – $1,001 | $1,760 – $3,840 |
| 5" | 5.43 yd³ | 245 | $739 – $1,207 | $2,000 – $4,080 |
| 6" | 6.52 yd³ | 294 | $875 – $1,414 | $2,240 – $4,320 |
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.
16×20 concrete slab: what to expect
A 16×20 slab covers 320 square feet. At the standard 4" thickness it takes about 4.35 cubic yards of concrete once you allow 10% for waste, which is roughly 196 × 80 lb bags if you mix by hand. Stepping up to 6" — sensible if it'll carry a vehicle — raises that to about 6.52 cubic yards.
Budget around $1,760 – $3,840 to have a 4" slab this size poured and finished by a contractor, or roughly $603 – $1,001 in ready-mix if you're doing the labor yourself. On top of the concrete you'll need about 4.54 yd³ of gravel base and 23 sticks of rebar.
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: