Concrete slab cost calculator

Enter the size, the thickness and what the slab is for. We price the bags, the gravel, the mesh and the forms at the store, set ready-mix by the yard beside them and show the installed range where we have one.

A 120 sq ft slab 4 in thick takes 1.63 cu yd. Mixed from bags, the materials come to $1,142.70 ($9.52 per sq ft). With ready-mix instead of bags, about $859 to $908. Hired out, $480 to $1,440.

Bags, DIY: 74 bags of 80 lb, $478.78 for the concrete, $291.15 per cu yd
Ready-mix, delivered: 1.63 cu yd at $120.00 to $150.00: $196 to $244 for the concrete
Installed, per sq ft: $4.00 to $12.00 (HomeGuide, Concrete patio cost, plain concrete (page dated Jul 10, 2025), read Nov 6, 2026)

At this size the bags cost about as much as ready-mix or more, and 74 bags is 3.0 tons to mix by hand. Past 1 cu yd, about 45 bags, a truck is the usual way to buy it. Ask the plant for its price and its minimum load, since a short-load fee often applies.

Material list for a slab mixed from bags. Type a price in any row to use your own.
Item	Qty	Line total
Quikrete 80 lb concrete mix	74 bag	$478.78
Gravel base, 0.5 cu ft bags	88 bag	$569.36
Concrete wire mesh sheet, 3.5 x 7 ft	6 sheet	$65.28
2 x 4 x 8 ft formwork boards	6 board	$29.28

Shelf prices from Home Depot, Hamilton Mill, and Concrete wire mesh sheet from Lowe's near Chamblee, GA, read Oct 8, 2026 to Nov 6, 2026, before tax and delivery. Ready-mix is HomeGuide's national range, read Nov 6, 2026.

Quantities only: concrete slab calculator

Cubic yards, 80 lb and 60 lb bags, gravel base, mesh or rebar and control joint spacing, without prices.

Planning figures for a slab on grade, not an engineer's design. Prices are shelf prices read on the dates shown; ready-mix and installed ranges are a named source's national figures. Call 811 before you dig, and check local rules for thickness, base and reinforcing.

How the concrete slab cost calculator works

Enter the size, the thickness and what the slab is for. The calculator works out the cubic yards with 10% extra, then prices the slab three ways: mixed from 80 lb bags with every other item on the list, poured from a ready-mix truck, and hired out at an installed rate per square foot. The gravel base, the wire mesh or rebar and the 2x4 forms are the same in the first two, so the only line that changes is the concrete.

What the slab is for sets the thickness

A patio, a walkway or a shed pad starts at 4 in. A garage floor or a pad where a car parks starts at 6 in, the top of the 5 to 6 in range people pour under a vehicle. Change the thickness if your plans or your building department say otherwise; the price follows the concrete.

Concrete slab cost by size

Slab	Concrete	Materials, from bags	With ready-mix	Installed
10x10 ft patio, 4 in	1.36 cu yd, 62 bags	$958.72	$721 to $761	$400 to $1,200
10x12 ft patio, 4 in	1.63 cu yd, 74 bags	$1,142.70	$859 to $908	$480 to $1,440
12x12 ft shed pad, 4 in	1.96 cu yd, 88 bags	$1,360.62	$1,026 to $1,085	$576 to $1,152
20x20 ft patio, 4 in	5.43 cu yd, 245 bags	$3,742.85	$2,810 to $2,973	$1,600 to $4,800
20x20 ft garage floor, 6 in	8.15 cu yd, 367 bags	$4,532.19	$3,135 to $3,380	$2,000 to $3,600
24x24 ft garage floor, 6 in	11.73 cu yd, 528 bags	$6,505.29	$4,497 to $4,849	$2,880 to $5,184

All rows use welded wire mesh, a 4 in gravel base in bags and 2x4 forms, before tax and delivery. The ready-mix column is the concrete at HomeGuide's range plus the same base, mesh and forms. We have no named installed rate for a shed pad or a garage floor yet, so those rows say so rather than borrow the patio figure.

Bags or ready-mix

The price per cubic yard

45 bags of 80 lb mix make a cubic yard. At $6.47 a bag that is $291.15 per cubic yard, against $120.00 to $150.00 for ready-mix delivered. So bags cost more per yard, but a small order from a plant often carries a short-load fee, which can wipe out the difference on a slab under a yard. Ask the plant for its price, its minimum load and the fee.

The work

A 10x12 ft patio at 4 in is 74 bags, about 3 tons to lift and mix. A 20x20 ft garage floor at 6 in is 367 bags, which is a truck job. Past about a cubic yard, plan for ready-mix, a crew of helpers and a screed, or hire it out.

What the price leaves out

The material list leaves out digging the base, hauling away the soil, a plate compactor, a mixer rental, finishing tools, a concrete pump where the truck cannot reach, delivery and sales tax. A garage floor may also need a vapor retarder and a permit; check with your building department.

Other ways to look at the same slab

For the quantities alone, with the bag count, gravel tons and control joint layout, use the concrete slab calculator. To set a concrete patio against pavers, stamped concrete or flagstone, use the patio cost calculator. The guide to concrete patio cost walks through common patio sizes, finishes and what a contractor's quote includes.

Where the numbers come from

Quantities come from our concrete slab calculator and the material list from the concrete mode of the patio cost calculator, so the three pages agree. The 80 lb Quikrete mix is the Home Depot Hamilton Mill shelf price (ZIP 30011), read Oct 13, 2026; the 2x4 form boards and the paver base come from the same store, and the wire mesh and No. 3 rebar from Lowe's near Chamblee, GA. Bag yields are Quikrete's: 0.6 cu ft for an 80 lb bag.

Ready-mix at $120.00 to $150.00 per cubic yard delivered is from HomeGuide, Stamped concrete cost (page dated Dec 23, 2025): concrete prices are $120 to $150 per cubic yard delivered for grades from 2,000 to 5,000 PSI, read Nov 6, 2026. The installed range, $4.00 to $12.00 per sq ft, is HomeGuide, Concrete patio cost, plain concrete (page dated Jul 10, 2025), read Nov 6, 2026, for patios and walkways. For a shed pad it uses $4.00 to $8.00 per sq ft and for a 6 in garage floor $5.00 to $9.00, both from This Old House, read Nov 7, 2026. The one-pallet threshold for bags follows Sakrete: about 45 bags of 80 lb make a cubic yard. The starting thicknesses, the 10% waste and the 4 in gravel base are editorial.

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Questions

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Questions people ask

A 10x10 ft slab at 4 in thick is 1.36 cu yd with 10% extra. Mixed from 62 bags of 80 lb at $6.47, with the gravel base, wire mesh and form boards, the materials come to $958.72. Hired out as a patio, HomeGuide's $4.00 to $12.00 per sq ft comes to $400 to $1,200.

At 4 in thick, a 20x20 ft slab is 5.43 cu yd. In bags that is 245 bags of 80 lb, and the materials list comes to $3,742.85. With ready-mix at $120.00 to $150.00 per cu yd instead of bags, about $2,810 to $2,973. As a 6 in garage floor it takes 8.15 cu yd: $3,135 to $3,380 with ready-mix.

Per cubic yard, ready-mix is. 45 bags of 80 lb make a cubic yard, which is $291.15 at $6.47 a bag, against HomeGuide's $120.00 to $150.00 per cubic yard delivered. Bags still make sense on a small slab, where a plant may add a short-load fee, so ask for the fee; past about a cubic yard, ready-mix is the cheaper and easier buy.

Installed, HomeGuide lists $4.00 to $12.00 per sq ft for a plain concrete patio (read Nov 6, 2026). Mixed from bags yourself, a 4 in slab runs about $9.52 per sq ft in materials on a 10x12 ft slab, before tax, delivery and tool rental.

About half as much concrete again: a 10x10 ft slab takes 1.36 cu yd at 4 in, 1.70 at 5 in and 2.04 at 6 in. The gravel, mesh and forms stay the same, so the materials go from $958.72 to $1,152.82 mixed from bags.