Concrete Slab Cost Calculator

How much does it cost to pour a concrete slab?

The cost to pour a slab is the concrete you order plus everything around it. Concrete is sold by the cubic yard, so the size and thickness fix the first line of the bill, and your local quotes fill in the rest. We do not publish a national average price because ready-mix and labor prices vary widely by region and season.

Slab cost = ordered yd³ × price per yd³ + delivery and short-load fees + labor (ft² × rate) + base, rebar and extras

The calculator above does exactly this. It works out the yards (adding 10% and rounding up to the next ¼ yd³), multiplies by the price you enter, adds your fees and labor rate, and shows the total and the price per square foot.

1. Measure the slab inside the forms and decide the thickness.
2. Call two or three ready-mix plants for the price per yard of the mix you need, their minimum load and the fee below it.
3. Ask contractors for itemized quotes so you can enter labor per square foot and extras separately.
4. Enter the numbers and compare totals for different thicknesses or finishes.

Concrete to order for common slab sizes

Most people search by size: “cost of a 20×20 slab”, “12×12 slab cost”, “30×30 slab 4 in thick”. The table gives the concrete volume for each size at 4 in, the amount to order, and how much each $100 of your yard price adds. Multiply that last column by your quote ÷ 100.

At 6 in thick every volume is 1.5 times larger. A 24 × 24 ft slab at 6 in is 10.67 yd³ (order 11¾ yd³) and a 40 × 60 ft slab is 44.44 yd³ (order 49 yd³).

What changes the cost of a concrete slab?

Thickness, the ready-mix price and site work drive most of the total. The concrete itself is often a smaller share than people expect.

• Price per yard. Set by your local plant. Ask for the strength you need, for example 3,000 or 4,000 psi, and whether fiber, color or set accelerators cost extra.
• Small-load fees. Many plants charge extra when an order is below their minimum load. On a ¼–2 yd³ pad this fee can cost more than the concrete. Ask each plant for its threshold and fee.
• Delivery distance and waiting time. Trucks usually include a set unloading time. Extra minutes, weekend pours and long hauls may be billed.
• Access. If the truck cannot reach the forms you pay for a pump, a power buggy or extra wheelbarrow labor.
• Site prep. Excavation, compacted gravel base and forms. The gravel calculator gives tons for the base.
• Reinforcement. Rebar, wire mesh or fiber. The rebar calculator sizes a grid.
• Finish. Broom finish is the simplest. Stamped, colored and exposed-aggregate finishes add labor and materials.
• Permits and inspections for garages, foundations and work near property lines, depending on your jurisdiction.

How much does slab cost per square foot?

Divide the total by the area. Concrete per square foot depends only on thickness and your yard price: at 4 in, 1 yd³ covers 81 ft², so each $100 of yard price is about $1.23 per ft² before waste. With 10% extra and rounding, the table shows $1.36 to $1.56 per ft² for each $100, higher on small slabs because rounding up to the next ¼ yard matters more. For other thicknesses and project types, see the concrete cost per square foot matrix.

Labor is usually quoted per square foot. Enter it in the calculator and it shows the combined price per square foot, so you can compare a contractor’s all-in square-foot quote with your own breakdown.

Is it cheaper to pour concrete yourself?

It can be for small slabs. You save labor but take on the risk of a poor finish, and the materials and fees stay the same.

• Under about ½ yd³: bags are practical. A 4 × 4 ft pad needs 10 × 80 lb bags with extra, and there is no delivery fee.
• About ½–2 yd³: compare a small-load delivery with 25–99 × 80 lb bags (10% extra included) plus a rented mixer. One yard is 45 × 80 lb bags, about 3,600 lb of dry mix.
• Over 2 yd³: ready-mix is almost always less work, and a crew finishes the slab before it sets. Large pours mixed by hand risk cold joints.

How much does a concrete pad cost?

A concrete pad costs the ordered yards × your yard price, plus any small-load fee, forms, base and labor. A 10 × 10 ft pad at 4 in orders 1½ yd³, so every $100 of yard price adds $150. Small pads are where fees and rounding hurt most. The concrete line per square foot on a 3 × 3 ft pad is about double that of a 20 × 20 ft slab, because a ¼ yd³ order is the smallest step and most of it is spare.

Decision rule for a pad: if the bag count with 10% extra is under about 25 × 80 lb bags (½ yd³), mix it yourself; between 25 and 99 bags (½–2 yd³ with extra), price both a small-load delivery and the bags; above that, order ready-mix. A hot tub pad is often specified thicker. An 8 × 8 ft pad at 6 in is 1.19 yd³, ordered as 1½ yd³, against 1 yd³ at 4 in. Check the tub maker’s installation sheet for the thickness it requires.

To compare a pad with a patio, driveway or sidewalk on a per-foot basis, the concrete cost per square foot page has a thickness × yard-price matrix.

Concrete patio cost: plain slabs

A plain broom-finished patio is a 4 in slab, so its concrete line follows the same arithmetic: a 12 × 16 ft patio orders 2¾ yd³ and a 16 × 20 ft patio 4½ yd³. Every $100 of yard price adds $275 and $450 respectively. For stamped or colored patios, which add a separate decorative labor line, use the concrete patio cost page.

Garage floor cost: 4 in vs 6 in

Garage slabs are where thickness choices move the bill most. The table gives the order at both thicknesses and the extra concrete for each $100 of your yard price. Your building department sets the minimum for a garage, so check local code before you choose.

On a 24 × 24 ft slab the concrete per square foot rises from about $1.39 to $2.04 for each $100 of yard price. Labor per square foot changes less, so the all-in increase is smaller than 50%. With an example $100/yd³ and $5/ft² labor, the 6 in 24 × 24 ft slab totals $1,175 + $2,880 = $4,055, about $7.04 per ft², before base and reinforcement.

Basement floor and house slab cost

A basement floor is usually poured inside existing walls, so the truck often cannot reach it. Budget for a pump or a chute and buggies, and ask the plant or a pump operator for that rate. The concrete at 4 in is straightforward:

• 24 × 30 ft basement (720 ft²): 8.89 yd³, order 10 yd³
• 30 × 40 ft basement (1,200 ft²): 14.81 yd³, order 16½ yd³
• 28 × 48 ft basement (1,344 ft²): 16.59 yd³, order 18½ yd³

A house slab on grade adds thickened edges or footings to the same floor area, so its volume is higher than the floor alone. The slab foundation cost page adds footings to the count.

Slab reinforcement estimate

Reinforcement is a separate line on most quotes. To check it, count the bars in a grid. The figures below use bars at 18 in or 12 in on center both ways, 3 in in from the edges, plus 10% for laps and waste.

Weights use the ASTM A615 nominal 0.376 lb/ft for #3 and 0.668 lb/ft for #4. Tightening a 20 × 20 ft grid from 18 in to 12 in adds 12 bars of 20 ft. Bar size and spacing come from your plans or local code; the rebar calculator sizes other grids.

Gravel base and finish: the other lines

A compacted gravel base is priced by the ton. At 4 in deep with 10% extra, a 10 × 12 ft slab needs about 2.6 tons of crusher run, a 20 × 20 ft slab 8.7 tons and a 24 × 24 ft slab 12.5 tons, using a typical planning density of 1.6 tons per yd³. Use your supplier’s density if it differs.

The finish is labor. A broom finish is included in most basic quotes. Polished concrete floors, stamping, color and exposed aggregate are priced per square foot by the finisher, so ask for that rate separately and enter it as extras. Polishing is ground after the slab cures, so it is often a different contractor and a separate quote from the pour.

Slab cost in metric

Outside the US, ready-mix is sold per cubic metre. Area in m² × thickness in metres gives m³. A 20 m² slab at 100 mm is 2.0 m³ (2.2 m³ with 10% extra); at 150 mm it is 3.0 m³ (3.3 m³). The concrete line is the order × your price per m³. To compare with a US-style quote, 1 m³ is 1.31 yd³.

Common mistakes when pricing a concrete slab

Most budget overruns come from the quantity, not the price per yard. These are the errors we see most often.

1. Ordering the exact volume. A 20 × 20 ft slab at 4 in is 4.94 yd³ on paper, but uneven subgrade and spillage eat into that. Order 5½ yd³ (10% extra, rounded up to ¼ yd³) rather than 5.
2. Assuming the base is perfectly level. If the subgrade sits ½ in low across a 20 × 20 ft slab, the average thickness becomes 4.5 in and the volume rises to 5.56 yd³. The order jumps from 5½ to 6¼ yd³.
3. Pricing a 6 in slab at 4 in volume. A 24 × 24 ft garage slab goes from an 8 yd³ order to 11¾ yd³, so the concrete line rises by 3¾ × your yard price.
4. Ignoring the small-load fee. On a 2 yd³ pad, an example $100 fee on a $100/yd³ price makes the real price $150 per yard. Ask every plant for its minimum and fee.
5. Comparing quotes that cover different work. One quote may include base, forms and reinforcement while another does not. Ask for itemized lines before comparing square-foot prices.

How do I get accurate slab quotes?

Get the volume right first, then collect prices for the exact order.

1. Work out the order with the concrete slab calculator and round up to the next ¼ yd³.
2. Ask plants for the price per yard, the minimum load and its fee, delivery charges and the free unloading time.
3. Ask contractors whether their quote includes excavation, base, forms, reinforcement, finishing, sealing and removal of spoil.
4. Enter those figures above and test changes, such as 4 in versus 5 in, before you sign.

Slab cost calculator vs related calculators: which one to use

Use this page when you want a total price for a slab. If you only need the volume, the concrete slab calculator gives yards, cubic feet, m³ and bags without the cost fields. To compare plant quotes or understand fees, use the concrete price per yard page. For a specific project, the concrete patio cost, concrete driveway cost and slab foundation cost pages start with typical sizes and thicknesses and list the extras those jobs usually need, such as footings under a house or removal of an old drive.