Concrete Slab Cost Calculator
A 10 × 10 ft slab at 4 inches thick needs about 1.23 cubic yards of concrete (1.36 with 10% waste). At a 2026 average of roughly $160 per cubic yard delivered, that is about $220 in concrete before labor. Enter your size below for a full cost breakdown.
Slab dimensions
ft
in
ft
in
in
4″ for patios/walkways, 5–6″ for driveways.
%
Supply & pricing
$/yd
Optional extras
$
$
in
Total estimated cost
$217
$2.17 per sq ft · 1.36 cu yd of concrete
Concrete (with waste)
1.36 cu yd
Material cost
$217
Show the math
area = 100 sq ft
cubic yards = area × (4 ÷ 12) ÷ 27 = 1.23
+ 10% waste = 1.36 cu yd
total = material + labor + rebar = $217
How to use this calculator
- Enter the slab length and width in feet and inches.
- Set the thickness (4 inches is standard for patios and walkways).
- Choose ready-mix delivery or bags (40, 60 or 80 lb).
- Adjust the price per cubic yard or per bag to your local quote.
- Optionally add labor, rebar/mesh and a gravel base to see the full cost.
Formula
cubic yards = length × width × (thickness ÷ 12) ÷ 27 × (1 + waste%)
bags = ceil(cubic feet ÷ bag yield) (80 lb ≈ 0.60 cu ft)
total = material + labor × area + rebar × area
cost per sq ft = total ÷ area
Worked example
A 10 × 10 ft slab, 4 inches thick, 10% waste:
cubic yards = 100 × (4 ÷ 12) ÷ 27 = 1.23
with 10% waste = 1.36 cu yd (36.7 cu ft)
bags of 80 lb = 36.7 ÷ 0.60 = 62 bags
Reference tables
| Slab size | Cu yd @ 4" | Cu yd @ 6" |
|---|---|---|
| 10 × 10 ft | 1.23 | 1.85 |
| 12 × 12 ft | 1.78 | 2.67 |
| 20 × 20 ft | 4.94 | 7.41 |
| 24 × 24 ft | 7.11 | 10.67 |
| 30 × 30 ft | 11.11 | 16.67 |
Volumes exclude waste. A 30×30 slab at 4 inches is about 11.1 cubic yards; add 10% and order 12.2.
Tips & buying advice
- Add about 10% waste for spillage, uneven subgrade and over-excavation.
- Bags make sense under roughly 1 cubic yard; above that, ready-mix delivery is usually cheaper and far less work.
- Ask about the ready-mix short-load fee — small orders under about 3–4 cubic yards often carry a surcharge.
- A 4-inch slab suits patios and walkways; driveways and garage floors are usually 5–6 inches. Confirm with local code.
Frequently asked questions
How much does a 20×20 concrete slab cost?
A 20×20 ft slab at 4 inches needs about 5 cubic yards of concrete. Material runs roughly $800–$1,000, and with finishing labor, rebar and base the installed cost is often $2,400–$4,000 depending on your area.
Is it cheaper to mix bags or order ready-mix?
Bags win only for small pours under about 1 cubic yard. A 10×10 slab takes around 60 bags of 80-lb mix — heavy, slow work. Above a yard, ready-mix delivery is cheaper per yard and much faster.
How thick should a concrete slab be?
Four inches is standard for patios, sheds and walkways. Driveways and garage floors are usually 5–6 inches, and heavy vehicle areas thicker. Always confirm against your local building code.
How many 80-lb bags of concrete are in a yard?
About 45 bags of 80-lb concrete mix make one cubic yard, since each bag yields roughly 0.60 cubic feet and a yard is 27 cubic feet. Sixty-pound bags take about 60 per yard.
Do I need rebar or wire mesh in a slab?
Most slabs benefit from #4 rebar on a grid or welded wire mesh to control cracking, especially driveways and anything bearing loads. Thin, lightly loaded pads can sometimes use fiber-reinforced mix instead.
What is the minimum ready-mix order?
Many suppliers deliver a minimum of about 1 cubic yard and add a short-load fee below roughly 3–4 yards. Ask when you order so a small slab does not cost more than you expect.
Related calculators
Landscaping Material
Open calculator →Cubic Yard Calculator
Area and depth to cubic yards, tons and bags for any loose material.
Concrete & Block
Open calculator →Concrete Block Calculator
How many CMU or cinder blocks a wall needs, plus mortar and cost.
Concrete & Block
Open calculator →Block Wall Calculator
Courses, blocks, cap, mortar, grout, rebar and total cost.
Landscaping Material
Open calculator →Square Yard Calculator
Convert feet and rooms to square yards, with waste and cost.
Sources
- QUIKRETE: Concrete Mix No. 1101 — product data sheet (80 lb ≈ 0.60 cu ft) — accessed October 8, 2026
- SlabCalc (2026 cost guide): Concrete Cost Per Yard — 2026 ready-mix prices ($145–195/yd³) — accessed October 8, 2026
Built and maintained by Sikander Mushtaq. Formulas checked against 2026 ready-mix price guides, Quikrete/Sakrete bag yields. See our methodology and sources, or learn about YardageMath.
Last updated:
Estimates only. Confirm quantities with your supplier or contractor. Read the full disclaimer.