Concrete slab cost = cubic yards × price per yard + delivery + base + reinforcement + labor + finishing. The calculator works out the yards from your slab size and thickness, multiplies by your quotes, and gives the total, the cost per square foot and the all-in cost per cubic yard. As a public reference point, South Dakota DOT's 2024 average low bid for 4 inch concrete sidewalk was $10.82 per square foot installed.
This is for homeowners pricing a patio, shed base, driveway or garage floor, and for anyone checking a contractor's quote line by line. It deliberately has no built-in "national average" for ready-mix. Local prices vary, and we only show numbers that come from a citable public source.
How to use the slab cost calculator
- Enter the slab size as length × width, or as square feet, plus the thickness in inches.
- Set the extra concrete percentage. 10% is our planning assumption, to cover an uneven subgrade and what stays in the chute.
- Enter the price per cubic yard from your ready-mix plant, plus any short-load or delivery fee.
- Add the optional lines that apply: gravel base depth and price per ton, rebar or mesh, labor, decorative finish, and a lump sum for forms, a pump or a permit. Leave the rest blank.
- Read the total, cost per ft² and all-in cost per yd³. Compare them with the SDDOT bid benchmark in the panel.
How slab cost is calculated
Concrete volume is length × width × thickness ÷ 324 (feet × feet × inches ÷ 324 = cubic yards, because 1 yd³ = 27 ft³ per NIST Handbook 44). Then:
- Concrete: yd³ × (1 + extra %) × your price per yd³
- Gravel base: area × base depth ÷ 324 = yd³ of base, × 2,850 lb/yd³ ÷ 2,000 = tons. This is the loose dry gravel midpoint from US Army FM 5-434, Table 1-2. Compacted base needs more stone, so ask your supplier for a compacted factor.
- Per-square-foot lines (reinforcement, labor, finish): rate × area.
- Cost per ft² = total ÷ area; all-in cost per yd³ = total ÷ yards ordered.
Concrete price per sq ft: public bid data
State transportation departments publish what contractors actually bid on public contracts. South Dakota DOT's 2024 Bid Item Price Report covers every contract let and awarded from January 1 to December 31, 2024. It lists the average unit low bid (the winning price) and the average of the three lowest bids for each item:
| Item | Description | Avg low bid | Avg of 3 lowest | Contracts | Implied $/yd³ of slab |
|---|---|---|---|---|---|
| 651E0040 | 4" concrete sidewalk | $10.82 | $11.17 | 14 | $876 |
| 651E0060 | 6" concrete sidewalk | $9.07 | $9.45 | 10 | $490 |
| 651E0140 | 4" reinforced concrete sidewalk | $15.78 | $23.51 | 4 | $1,278 |
| 651E0160 | 6" reinforced concrete sidewalk | $18.17 | $20.88 | 4 | $981 |
Read these with care. They are public-works sidewalks bid by commercial contractors in one state, and they include labor, forming, finishing, overhead and profit. The 6 in sidewalk came in cheaper per square foot than the 4 in. That reflects the projects bid that year (bigger jobs get lower unit prices), not concrete getting cheaper as it gets thicker. The last column divides the bid price by the yards in one square foot of slab. It shows the installed cost per cubic yard, which is far above a delivered ready-mix price.
Cost of a yard of concrete: what public data can and can't tell you
No government source publishes a residential ready-mix price per cubic yard. Here is what is available, and what each figure means:
- BLS Producer Price Index for ready-mix concrete (series PCU327320327320, June 1981 = 100). It tracks the change in prices received by ready-mix producers, not the price level. The index was 390.897 on average in 2024, 393.679 in August 2025 and 402.65 in August 2026 (preliminary). That is up 2.3% in a year and 3% since 2024. Use it to update an old quote, not to create a new one.
- USGS cement price. The Mineral Commodity Summaries 2026 put the average mill unit value of cement at $160 per metric ton in 2025. That is cement powder at the plant gate. Concrete is mostly sand and stone.
- DOT structural concrete bids. SDDOT's Class A45 box-culvert concrete averaged $1,011.32 per yd³ in 2024. That is concrete placed in forms on a highway structure, so it isn't a material price.
Cement $/ton is not concrete $/yd³
Monroe County DOT's sidewalk and driveway spec (Class K) calls for 564 lb of cement per cubic yard. At the USGS mill value, that much cement costs 564 ÷ 2,204.62 lb per tonne × $160 = $40.93 per yard. A delivered yard of concrete also pays for aggregates, water, admixtures, batching, the mixer truck and driver, and the plant's margin. A cement price can only tell you the floor for one ingredient, so get the real number from a supplier.
Worked example (hypothetical quote numbers)
The prices below are made-up example quotes to show the math. They are not market prices. A 20 × 20 ft patio, 4 in thick, with 10% extra needs 5.43 yd³. Suppose the quote is $200 per yard, the base is 4 in of gravel at $40 per ton (7 tons), mesh is $0.50 per ft², labor is $4.00 per ft², and $150 covers forms:
| Line | Cost |
|---|---|
| Ready-mix concrete | $1,086.42 |
| Gravel base | $281.48 |
| Rebar or mesh | $200.00 |
| Labor (place & finish) | $1,600.00 |
| Other (forms, permits, pump) | $150.00 |
| Total | $3,317.90 |
That works out to $8.29 per ft² and $611 per cubic yard all-in. Change any line in the calculator to see its effect.
Concrete-only cost per square foot by thickness
To turn a price per yard into a concrete-only price per square foot, multiply by the yards in one square foot: 0.0123 at 4 in, 0.0154 at 5 in and 0.0185 at 6 in. The table applies these factors to round example prices (not market data), with no extra concrete included:
| Price per yd³ | 4 in slab | 5 in slab | 6 in slab | 8 in slab |
|---|---|---|---|---|
| $100 | $1.23/ft² | $1.54/ft² | $1.85/ft² | $2.47/ft² |
| $125 | $1.54/ft² | $1.93/ft² | $2.31/ft² | $3.09/ft² |
| $150 | $1.85/ft² | $2.31/ft² | $2.78/ft² | $3.70/ft² |
| $175 | $2.16/ft² | $2.70/ft² | $3.24/ft² | $4.32/ft² |
| $200 | $2.47/ft² | $3.09/ft² | $3.70/ft² | $4.94/ft² |
| $225 | $2.78/ft² | $3.47/ft² | $4.17/ft² | $5.56/ft² |
| $250 | $3.09/ft² | $3.86/ft² | $4.63/ft² | $6.17/ft² |
| $300 | $3.70/ft² | $4.63/ft² | $5.56/ft² | $7.41/ft² |
Common mistakes when pricing a slab
- Comparing a materials price with an installed price. A per-yard ready-mix quote and a per-square-foot contractor bid measure different things. Convert both to cost per square foot before comparing them.
- Leaving out the short-load fee. On small pours it can be the biggest single line.
- Pricing the nominal thickness only. Thickened edges, low spots and extra for waste all add yards.
- Ignoring the base. Gravel, compaction and excavation are part of the job even though they aren't concrete.
- Using a cement price as a concrete price. Cement per ton is roughly an order of magnitude away from concrete per yard.
To get just the volume, including footings, walls, columns and steps, use the concrete calculator. For gravel or fill under the slab, try the cubic yard calculator. Paving instead? See the asphalt calculator, and for a whole remodel budget the renovation cost calculator.
Frequently asked questions
How much does a concrete slab cost per square foot?
Public bid data gives a benchmark. In South Dakota DOT's 2024 contracts, the average low bid for 4 in concrete sidewalk was $10.82 per ft² across 14 contracts, and $9.07 for 6 in. Reinforced 4 in sidewalk was $15.78. Those are installed prices for public work. For your own slab, enter local quotes into the calculator for a cost per square foot.
How much does a yard of concrete cost?
No federal agency publishes a retail ready-mix price per cubic yard, so this calculator has no default. Ask your local plant for a quote per yard plus any short-load or delivery fee. As a reference point, the BLS producer price index for ready-mix concrete was 3% higher in August 2026 (preliminary) than its 2024 average, and 2.3% higher than a year earlier.
What does 1 yard of concrete cost if I use bags instead?
A yard is 45 bags of 80 lb premix (0.60 ft³ each, per QUIKRETE). Multiply 45 by the shelf price per bag and compare it with your ready-mix quote including the short-load fee.
Is cement price the same as concrete price?
No. USGS reports the 2025 average mill value of portland cement at about $160 per metric ton. Cement is only one ingredient. A sidewalk mix with 564 lb of cement per yard (Monroe County DOT Class K) contains about $40.93 of cement at that mill price, before sand, stone, water, admixtures, batching, delivery and profit.
How many square feet does a yard of concrete pour?
At 4 in thick, one yard covers 81 ft²; at 5 in, 64.8 ft²; at 6 in, 54 ft². So your cost per square foot for the concrete alone is the price per yard ÷ 81 at 4 in, or the price per yard × 0.0123.
Why do small concrete orders cost more per yard?
Ready-mix plants usually set a minimum load. Smaller orders often carry a short-load or small-load fee, plus waiting-time charges if the truck stands too long. That is why the calculator has a separate delivery and short-load line. Check the fee with your supplier, because it can cost more than the concrete in a one-yard order.
Does a gravel base add much to the cost?
It adds material and labor. A 4 in gravel base under a 20 × 20 ft slab is about 7 tons of loose gravel at 2,850 lb/yd³ (the midpoint in US Army FM 5-434), before compaction. Enter the depth and your price per ton in the calculator.
How do I compare two contractor quotes?
Ask each one for slab thickness, the mix strength or class, whether rebar or mesh is included, the base depth, and whether forming, finishing, sealing and cleanup are in the price. Then enter each one's line items and compare the cost per square foot. Two quotes that look different often just cover different scope.
Why is DOT concrete so expensive per yard?
SDDOT's Class A45 box-culvert concrete averaged $1,011.32 per yd³ in 2024. That price is for structural concrete placed in forms on a highway job, including labor, forming and overhead. It isn't the price of a yard of ready-mix delivered to your driveway, and it shouldn't be used as one.
Sources & method
- South Dakota DOT, 2024 Bid Item Price Report (published March 31, 2025): items 651E0040–651E0160 concrete sidewalk, 460E0120 Class A45 concrete
- U.S. Bureau of Labor Statistics, PPI by Industry: Ready-Mix Concrete Manufacturing (PCU327320327320)
- U.S. Geological Survey, Mineral Commodity Summaries 2026: Cement (average mill unit value, $/metric ton)
- Monroe County (NY) DOT specification C608.0101, Concrete Sidewalk and Driveway: Class K mix, 564 lb cement per cubic yard
- US Army FM 5-434, Earthmoving Operations, Table 1-2: loose gravel 2,700–3,000 lb/yd³
- NIST Handbook 44 (2026), Appendix C: 1 yd³ = 27 ft³; 1 lb = 0.45359237 kg
Results are estimates for general information. Found an error? It helps everyone — see our methodology.