Concrete Slab Cost Calculator

How to use this calculator

1. Enter the slab's length, width and thickness. Four inches is the usual residential figure and the IRC minimum is 3-1/2.
2. Leave the waste allowance at 10 percent unless you have a reason. NRMCA says to order "at least 4 to 10 percent" more than the plan volume.
3. Edit the prices. They are US-average defaults reviewed as of 2025, not quotes. Delivered ready-mix is $160 per cubic yard here; call one supplier and you will have a better number in five minutes.
4. Read the range, not the midpoint. The labor band runs $2 to $8 per square foot because finish, reinforcement and site access swing it that far.
5. On anything under about 400 square feet, compare the total against $1250 and take the higher figure. See the next section for why.

What the calculator leaves out, and it is the biggest number on a small slab

This calculator does what every slab cost calculator does: it multiplies a volume by a price, multiplies an area by a labor rate, and adds them. That model is right at 400 square feet and up. Below that it misses the largest single term in the bill, which is the cost of a crew showing up at all.

Almost nobody publishes that figure. One contractor does, twice, in dollars. Day's Concrete Floors in Maine states "I have a minimum charge for labor of $1,250.00 dollars for small slabs under 20' x 20'" and elsewhere "a minimum labor charge might be $1500 dollars for a 10 x 10 slab as well as $1600.00 for an 18 x 12 slab." He also says why: "Whether the concrete slab is 10' x 10' or 16' x 12', the time (labor) is pretty much the same."

Two aggregators put a minimum at $500 to $900, and the same publisher gives two different figures on two of its own pages. A contractor-software vendor's worked travel and setup example comes out near $400. The contractor-side figures are two to four times the aggregator-side ones, and the contractor is the one sending the invoice.

The middle column is the concrete at the $160 per yard list rate. The calculator's own figure is higher than material plus labor alone, because below a 10 yard truck minimum it adds a $30 per yard short load surcharge, which is right in direction even though real suppliers bill it as a flat fee per load rather than per yard.

So on a 10 by 10 the calculator's figure and a real quote can be nearly a factor of two apart, and the error runs in the direction that costs you. By a 20 by 20 the floor has stopped binding and the calculator is the better model. Concrete slab cost by size has the full curve, the published by-size tables and why eight of thirteen cost guides print a single rate from 25 square feet to 2,400.

Why not just build the floor into the calculator? Because it is one contractor's figure from one state, it is labor only, and it would be wrong in both directions depending on your market. Showing it next to the arithmetic is more honest than burying it inside the arithmetic.

What drives the cost to pour a slab

Square footage, and not linearly. The per-foot rate falls as the slab grows, for three compounding reasons: the minimum job charge above; the concrete being billed at a multiple of list below one cubic yard; and forming being priced by the perimeter, which grows linearly while area grows as the square. Doubling a square slab's side quadruples the area and only doubles the edge, so forming cost per square foot falls about fivefold from a 10 by 10 to a 40 by 60 from geometry alone.

Thickness, which is concrete and almost nothing else. A cubic yard covers 81 square feet at 4 inches, 65 at 5 and 54 at 6, so at the default $160 per yard the concrete runs $1.98, $2.47 and $2.96 per square foot respectively. There is no published labor premium for a thicker slab. The one contractor who publishes both rates charges $12.50 per square foot at 6 inches and $12.00 at 4, a $0.50 difference against $0.93 to $1.18 of extra concrete, so he charges less for the extra two inches than they cost him. How thick should a concrete slab be covers when 4 is not enough.

Finishing labor, which is most of the bill. The default band here is $2 to $8 per square foot, with $4.5 as the typical figure. The Bureau of Labor Statistics puts cement masons and concrete finishers at a median of $27.41 an hour with a 90th percentile of $41.10, and a professional estimating manual puts a cement mason's fully burdened cost at $35.34 with the burden disclosed at 22.92 percent. Every source in this topic except one agrees labor is the majority of a slab bill: 56 percent in one contractor's own itemization, 70 to 79 percent on decorative work.

Reinforcement, which is cheaper than the cost guides claim. Welded wire mesh installed is $0.83 to $0.98 per square foot on a disclosed 534 square foot basis; the mesh material alone is $0.36 to $0.52. Fiber is an admixture at $7.50 to $8.00 per cubic yard, which at 81 square feet per yard is about $0.09 to $0.10 per square foot, and one major aggregator prices it at $2 to $3, twenty to thirty times too high. The rebar calculator prices a bar grid from current prices and rebar, mesh and vapor barrier covers which you actually need.

Everything under the slab, which is probably not in your quote. The two sources in this topic that state their scope both exclude excavation, the gravel base and compaction. One of them prices that work separately at $5.00 per square foot, which on a 960 square foot job was $4,800 against an $11,520 slab. Published figures for the same layer run from $0.38 to $5.00 per square foot, a factor of thirteen, which is wider than the published spread on the finished slab. Ask whether it is in the number.

Access and pumping. A line pump is $150 to $250 an hour, a boom pump $200 to $300 or more, both with minimums covering the first two to four hours; one contractor adds a flat $1,500 and leaves it at that. Ready-mix delivery has the rest of the fee schedule, including waiting time at $2 to $5 a minute once the truck has been there 5 to 7 minutes per yard.

Below one cubic yard, the concrete price stops being the concrete price

The calculator's short load handling uses a $30 per cubic yard surcharge below a 10 yard truck minimum, which is a conservative national default. What suppliers actually publish is a flat fee per load, commonly $90 to $175, with minimum order thresholds from 2 to 6 cubic yards. The difference matters most on a small pad.

Measured across seven suppliers in five states, the effective price of the concrete alone, per cubic yard placed:

It stops mattering at about five cubic yards, which is a 20 by 20 slab at 4 inches. Below one yard it dominates everything else on this page. Concrete pad cost has the supplier-by-supplier detail, including the Michigan supplier who charges no short load fee at all and still reaches 10 times list at a 4 by 4 because of his 2 yard minimum alone.

Bags against ready-mix

The calculator shows both. Forty-five 80 lb bags make one cubic yard at the published 0.60 cubic foot yield, so at $8 a bag that is $360 per cubic yard of material before you have lifted anything. Against $160 delivered, bags lose on price well before they lose on effort.

Where bags win is below the supplier's minimum, because the minimum is what makes a small pour expensive rather than the price of the material. The crossover sits between roughly two thirds of a yard and two and a half yards depending on which brand of bag and which supplier, which is somewhere between an 8 by 8 and a 12 by 12 pad at 4 inches. There is also a labor ceiling: Sakrete publishes a maximum of two 80 lb bags per mixer batch at about five minutes a batch, which is twelve batches inside the one hour window it gives before you risk a cold joint. A 12 by 12 slab is 80 bags and over three hours of mixing. The bag calculator and bags per yard have the arithmetic.

Slab cost reference

Four published answers to "what does a slab cost per square foot," which is the honest way to show it, because they do not agree and the disagreement is informative.

The two that disclose a basis quantity agree with each other: Homewyse's 129 square foot example at $10.63 to $13.00 and the contractor's 120 square foot slab at $14.92 land within 15 percent. The flat-rate consensus prices that same small slab at $6 to $12 and uses the same number for a slab twenty times the size.

Our own defaults, which drive the calculator above, are $160 / yd delivered and $2 to $8 per square foot of finishing labor, reviewed as of 2025. At 4 inches that is $1.98 per square foot of concrete, so the all-in default lands between about $4 and $10 per square foot at normal size. Edit them.

Related

Concrete slab cost by size is the companion guide, with the by-size curve, the state DOT bid tabs showing five contractors pricing the same item higher at low quantity, and the teardown of the published tables. The slab calculator sizes volume, reinforcement and base without pricing. The general cost calculator handles any shape. Pad cost is the one to use under a yard. Driveway cost, patio cost and concrete floor cost cover the project-specific versions, and foundation cost covers a whole house.