Updated April 2026

Concrete Slab Cost Calculator: Find Your Price by Size (2026)

Q: How do I calculate cubic yards for a concrete slab?

Use this formula: Cubic yards = (Length ft × Width ft × Thickness inches ÷ 12) ÷ 27. Example: A 20×20 ft slab at 4-inch thickness = (20 × 20 × 0.333) ÷ 27 = 2.47 cubic yards. Always add 10% for waste and overage. Our calculator above performs this calculation automatically.

Q: How accurate are these cost estimates?

The estimates are national averages based on 2026 US contractor pricing data, industry surveys, and publicly available quote compilations. They represent installed cost including labour, materials, forming, and basic finishing. They do NOT include: excavation, grading, demolition of existing concrete, permits, or decorative finishes (unless selected). Actual costs vary by 20–40% depending on location, site conditions, and contractor.

Q: What's not included in the cost estimate?

The calculator estimates installed slab cost including: concrete materials, reinforcement (if selected), forming, placement, and basic finishing. Not included: site excavation and grading ($500–$3,000+), demolition of existing slab ($2–$6/sqft), building permits ($50–$250), decorative coatings and epoxy flooring, drainage installation, and landscaping restoration around the slab.

Enter your slab dimensions to get an instant cost estimate with cubic yards required. Covers every standard residential size from 8×8 through 40×80.

Concrete Slab Cost Calculator

Width (feet)

Length (feet)

Thickness

Reinforcement

Finish

Region

How to Read This Table

Low: 4-inch plain broom finish, no reinforcement, standard 3,000 PSI mix. Suitable for shed pads and light patios.
Mid: 4-inch, wire mesh reinforcement, broom finish. Standard residential patio or parking pad.
High: 6-inch, rebar grid, suitable for driveways, garage floors, and heavy loads.
All estimates include labour. Exclude: excavation, permits, decorative finishes, demolition.
Regional variation: Northeast/CA add 20–35%; South Central/Southeast subtract 5–10%.

Complete Concrete Slab Cost Table

Slab Size	Sq Ft	Low (basic)	Mid (standard)	High (reinforced)	Cu Yds (4“)	Cu Yds (6“)	Typical Use
8×8	64	$256	$480	$768	0.79	1.19	Shed pad, AC unit
8×10	80	$320	$600	$960	0.99	1.48	Small shed pad
10×10	100	$400	$750	$1,200	1.23	1.85	Small shed, hot tub
10×12	120	$480	$900	$1,440	1.48	2.22	Shed / storage
12×12	144	$576	$1,080	$1,728	1.78	2.67	Patio / storage
10×16	160	$640	$1,200	$1,920	1.98	2.96	Single car parking
12×16	192	$768	$1,440	$2,304	2.37	3.56	Small patio
14×14	196	$784	$1,470	$2,352	2.42	3.63	Patio
10×20	200	$800	$1,500	$2,400	2.47	3.7	Small patio
12×20	240	$960	$1,800	$2,880	2.96	4.44	Standard patio
16×16	256	$1,024	$1,920	$3,072	3.16	4.74	Medium patio
12×24	288	$1,152	$2,160	$3,456	3.56	5.33	Patio / parking
16×20	320	$1,280	$2,400	$3,840	3.95	5.93	Large patio
18×18	324	$1,296	$2,430	$3,888	4	6	Medium patio
16×24	384	$1,536	$2,880	$4,608	4.74	7.11	Large patio
20×20	400	$1,600	$3,000	$4,800	4.94	7.41	Large patio / small garage
20×24	480	$1,920	$3,600	$5,760	5.93	8.89	Patio / sport court
24×24	576	$2,304	$4,320	$6,912	7.11	10.67	2-car garage floor
20×30	600	$2,400	$4,500	$7,200	7.41	11.11	Large patio / RV pad
24×30	720	$2,880	$5,400	$8,640	8.89	13.33	Large garage
30×30	900	$3,600	$6,750	$10,800	11.11	16.67	Large garage / workshop
24×40	960	$3,840	$7,200	$11,520	11.85	17.78	3-car garage
30×40	1,200	$4,800	$9,000	$14,400	14.81	22.22	3-car garage / outbuilding
30×50	1,500	$6,000	$11,250	$18,000	18.52	27.78	Workshop / outbuilding
40×60	2,400	$9,600	$18,000	$28,800	29.63	44.44	Small commercial
40×80	3,200	$12,800	$24,000	$38,400	39.51	59.26	Commercial / large garage

Worked Example: 20×20 Concrete Slab

A 20×20 ft slab is one of the most common residential sizes, large patio, single-car garage, or sport court pad.

400 sq ft

Area

$3,000

Mid estimate

at $7.50/sqft

2.47 cu yd

Concrete (4-inch)

3.70 cu yd

Concrete (6-inch)

As a patio: 4-inch, wire mesh, broom finish = $2,400–$4,000 total. Wire mesh recommended for patios with outdoor furniture.
As a garage floor: 6-inch, rebar grid = $3,200–$5,600 total. Rebar required for vehicle loads.
As a driveway: 4-inch minimum, wire mesh = $2,800–$5,000 total. Add $500–$1,000 for expansion joints and proper slope.

Standard Sizes by Project Type

Project	Standard Size	Approx Sq Ft
Small shed pad	8×10	80
Hot tub base	10×10	100
AC unit pad	3×3 to 4×4	9–16
1-car garage	12×20 or 14×20	240–280
2-car garage	20×20 or 24×24	400–576
Small patio	10×12 to 12×16	120–192
Standard patio	12×20 to 16×20	240–320
Large patio	16×24 to 20×30	384–600
RV parking pad	12×40 to 16×50	480–800
3-car garage	30×24 to 30×36	720–1080

Cubic Yards Quick Reference

Formula: (Length × Width × Thickness inches ÷ 12) ÷ 27 = cubic yards. Always add 10% for waste.

Slab Size	4-inch slab	6-inch slab	4” + 10% waste	6” + 10% waste
8×8 ft	0.79	1.19	0.87	1.31
10×10 ft	1.23	1.85	1.35	2.04
10×16 ft	1.98	2.96	2.18	3.26
10×20 ft	2.47	3.7	2.72	4.07
12×12 ft	1.78	2.67	1.96	2.94
12×16 ft	2.37	3.56	2.61	3.92
12×20 ft	2.96	4.44	3.26	4.88
14×14 ft	2.42	3.63	2.66	3.99
16×16 ft	3.16	4.74	3.48	5.21
16×24 ft	4.74	7.11	5.21	7.82
18×18 ft	4	6	4.40	6.60
20×20 ft	4.94	7.41	5.43	8.15

Calculator FAQ

What size concrete slab do I need for a 2-car garage?

A standard 2-car garage requires a slab of at least 20×20 ft (400 sq ft) for a tight fit, or 24×24 ft (576 sq ft) for comfortable door opening and walking space on each side. Most builders recommend 24×24 as the minimum for a 2-car garage. If you plan to add a workbench area, consider 24×30 or 24×36.

How do I calculate cubic yards for a concrete slab?

How accurate are these cost estimates?

What's not included in the cost estimate?

Patio Slab Cost Garage Floor Cost Driveway Cost Cost Factors