PourMath

Concrete material & cost calculator

Concrete Slab Calculator

Square or rectangular slabs, patios, sheds, garage floors.

Enter your dimensions

in
in
%

Order extra for spillage and uneven subgrade. 5–10% is standard.

$/yd³

Set your local rate to estimate material cost.

Pouring reinforced? Size the grid with the rebar calculator: sticks, linear feet, and weight.

Get quotes from local concrete pros

You've got the volume and a ballpark cost. The next step is real numbers: compare free, no-obligation quotes from licensed concrete contractors in your area for your slab.

Popular slab sizes

Jump to a pre-filled calculator for a common size:

4×4 ~0.2 yd³ 5×5 ~0.3 yd³ 6×6 ~0.5 yd³ 8×8 ~0.9 yd³ 10×10 ~1.4 yd³ 10×12 ~1.6 yd³ 10×20 ~2.7 yd³ 12×12 ~2.0 yd³ 12×16 ~2.6 yd³ 12×20 ~3.3 yd³ 12×24 ~3.9 yd³ 16×16 ~3.5 yd³ 16×20 ~4.3 yd³ 20×20 ~5.4 yd³ 20×24 ~6.5 yd³ 24×24 ~7.8 yd³ 24×30 ~9.8 yd³ 24×36 ~11.7 yd³ 30×30 ~12.2 yd³ 30×40 ~16.3 yd³ 40×60 ~32.6 yd³ 40×80 ~43.5 yd³

Slab cost by size

Concrete to order at 4″ thick (with 10% waste) and typical installed price ranges. Cost data updated June 2026.
SizeAreaConcreteInstalled range
4×4 slab16 sq ft0.22 yd³$96 – $192
5×5 slab25 sq ft0.34 yd³$150 – $300
6×6 slab36 sq ft0.49 yd³$216 – $432
8×8 slab64 sq ft0.87 yd³$384 – $768
10×10 slab100 sq ft1.36 yd³$600 – $1,200
10×12 slab120 sq ft1.63 yd³$720 – $1,440
10×20 slab200 sq ft2.72 yd³$1,200 – $2,400
12×12 slab144 sq ft1.96 yd³$864 – $1,728
12×16 slab192 sq ft2.61 yd³$1,152 – $2,304
12×20 slab240 sq ft3.26 yd³$1,440 – $2,880
12×24 slab288 sq ft3.91 yd³$1,728 – $3,456
16×16 slab256 sq ft3.48 yd³$1,536 – $3,072
16×20 slab320 sq ft4.35 yd³$1,920 – $3,840
20×20 slab400 sq ft5.43 yd³$2,400 – $4,800
20×24 slab480 sq ft6.52 yd³$2,880 – $5,760
24×24 slab576 sq ft7.82 yd³$3,456 – $6,912
24×30 slab720 sq ft9.78 yd³$4,320 – $8,640
24×36 slab864 sq ft11.73 yd³$5,184 – $10,368
30×30 slab900 sq ft12.22 yd³$5,400 – $10,800
30×40 slab1,200 sq ft16.30 yd³$7,200 – $14,400
40×60 slab2,400 sq ft32.59 yd³$14,400 – $28,800
40×80 slab3,200 sq ft43.46 yd³$19,200 – $38,400

Installed ranges are regional ballparks covering labor, forming, base, and finishing, not quotes. Click a size for its pre-filled calculator. See the full concrete slab cost guide for what drives the range.

Embed this calculator on your website

Free for any site: no signup, no ads. Copy the code below; please keep the attribution link.

About this calculator

A concrete slab is priced by volume, so the only numbers that matter are length, width, and how thick you pour it. Enter the dimensions below and you'll get the volume in cubic yards (how ready-mix is sold), the equivalent in bags for smaller pours, and a built-in waste allowance so you don't come up short halfway through.

How the math works

The math is simply length × width × thickness, with everything converted to the same unit. Slab thickness is entered in inches because that's how it's spec'd on site, then divided by 12 to turn it into feet before multiplying. That gives cubic feet; dividing by 27 converts to cubic yards.

Cross-section of a concrete slab on a gravel base, with 4-inch and 6-inch thickness

Common questions

How thick should a slab be?

4 inches is the standard for patios, walkways, and shed floors. Bump to 5–6 inches for driveways or anything carrying vehicle weight. Thickness drives volume directly, so going from 4" to 6" adds 50% to your concrete order.

Do I need to account for the slab edges?

If you're pouring a thickened edge or a footing around the perimeter, calculate that separately with the footing calculator and add the two volumes together.

What strength concrete?

Most residential slabs use 3,000–4,000 PSI mix. Your ready-mix supplier will ask, but it doesn't change the volume, only the price per yard slightly.

Concrete guides

Other concrete calculators