Concrete Pad Cost Calculator

The short load penalty, measured

Ready-mix suppliers charge for a minimum load whether you use it or not, and most add a fee on top for anything under their threshold. The thresholds published by real suppliers run from 2 to 6 cubic yards, and almost every residential pad falls under them.

Here is what that does to the price of concrete, using each supplier's own published rates and billing rules. The dollar figure is what the concrete in the pad actually cost per cubic yard; the multiple is against that supplier's own list rate.

Four things come out of that table, and all four are measurements rather than opinions.

The blow-up is concentrated under one cubic yard. At 1 to 2 yards the premium is 1.3 to 2.1 times list, which is survivable. Below half a yard it is 8 to 12 times, because that is where the minimum-load floor bites on top of the fee.

The mechanism is not regional even though the price is. Seven suppliers across four states span 8.0x to 11.9x at a 4 by 4 pad and 1.1x to 1.2x at 20 by 20. Their list rates vary by 60 percent; the penalty curve barely varies at all.

A supplier does not need a short load fee to punish a small pour. A minimum order does it alone. One Michigan supplier states plainly that it "INSISTS ON MINIMUM 2.0 YD3 ORDER" and charges no short load fee whatsoever. It still reaches 10.1 times list at a 4 by 4 pad, because you buy two yards and place a fifth of one.

About 5 cubic yards is where it stops mattering, which is exactly where three of the seven set their threshold. At 4 inches thick, that is a pad bigger than 20 by 20 feet.

The most granular schedule found is a five-step tier from one Ohio supplier: $165 per load at 1 to 1.75 yards, falling to $105 at 5 to 5.75. There is no tier below 1 yard, which is the floor doing its work. Others publish a flat $90, $95, $100, $120, $125 or $175 per load, and one California supplier publishes delivery of $120 to $350 per load across seven zones plus a minimum charge of $162 to $810.

One cost you cannot plan for: two suppliers publish standby at $2.00 a minute past an allowance of five minutes per cubic yard. On a one-yard load that allowance is five minutes, plus a twenty-minute grace from one of them. Nobody publishes how long a small residential pour actually takes, so the exposure is real and unquantifiable. Ask for the unload window in writing.

Bags or ready-mix, and where they actually cross

This is the decision the short load penalty forces, and it can be solved rather than guessed, because both sides publish their numbers.

Published yields are identical between the two major brands: 40 lb gives 0.30 cubic feet, 60 lb gives 0.45, and 80 lb gives 0.60. So a cubic yard is 90 bags of 40 lb, 60 bags of 60 lb or 45 bags of 80 lb, exactly. At independent retailer prices that works out at $269.55 to $377.55 per cubic yard of bagged material, depending which bag you buy.

So the honest answer is a band, not a number. Below about an 8 by 8 pad, bags win on material cost against every supplier checked. Above about a 12 by 12, ready-mix wins against every one of them. Between those two, it depends entirely on which bag you buy and which supplier you call.

Note what moves the answer most. Bag brand shifts the crossover by a factor of four; supplier choice shifts it by less than three. The cheap bag pushes it out past 2.7 yards and the premium bag pulls it in to 0.65. That is not what anyone expects, and it means the first thing to price is the bag, not the truck.

The constraint that actually binds, which is not money

One manufacturer publishes mixing throughput and it deserves far more attention than it gets. Its figures: one 80 lb bag per batch by hand, two bags per batch in a standard mixer, about five minutes a batch, and twelve batches inside the one hour window before cold joints form.

Run that out and a single mixer with one person places 14.4 cubic feet an hour, which is about 43 square feet of 4 inch pad, or roughly a 6.5 foot square. By hand it is half that. Against the quantities below:

• 8 x 8 pad: 36 bags, 2,880 lb to carry, about 1.5 hours of continuous mixing
• 10 x 10 pad: 56 bags, 4,480 lb, about 2.3 hours
• 12 x 12 pad: 80 bags, 6,400 lb, about 3.3 hours, more than three times the manufacturer's own one hour window

So even where bags are still cheaper at 12 by 12 against the dearer suppliers, they are not advisable. The maker's own advice at that point is to set up a second mixing station or split the pour into sections. The practical ceiling for one person and one mixer is a monolithic pad of about 6.5 feet square. Everything above that is a second person, a second mixer, or an accepted cold joint.

A rented mixer is $69 for an eight hour day at one published rate card, which shifts every crossover down by roughly a quarter of a yard. There is also no reason to rent the smaller drum: the 2 and 3 cubic foot electric mixers are the same price.

One detail worth having: that brand's hand-mixing page states an output of "7 sq.ft." where its own arithmetic gives 7.2 cubic feet, which at 4 inches is 21.6 square feet. Its mixer page does the identical calculation correctly, so trust the mixer page.

Quantities by pad size

Concrete and bags for the common pad sizes. Bags are 80 lb at the published 0.60 cubic foot yield, rounded up.

Read that against the published supplier thresholds and the scale of the problem is clear: at 4 inches, every pad up to and including 20 by 20 is a short load at a 6 yard threshold, and everything up to 12 by 16 is short of a 3 yard one. Only the two largest sizes here clear a 6 yard minimum. The small pad is not an edge case, it is almost the whole of the residential pad market.

For volume only, without the pricing, use the concrete pad calculator. For a different shape, the concrete yardage calculator handles slabs, footings, columns and circles.

What mix to order, and the requirement that actually bites

Most pad pages talk about psi. For an outdoor pad in a cold climate, strength is the easy half.

The IRC sets minimum compressive strength by exposure in Table R402.2. A freestanding pad is not named in it, so the honest reading is to take the nearest listed category, porches, carport slabs and steps exposed to weather, which gives 3,000 psi where weathering potential is moderate and 3,500 psi where it is severe. There is no listed category for weather-exposed concrete that would give a lower number, so treat that as the floor.

Now the part that matters. Footnote d to that table reads: "Concrete shall be air-entrained. Total air content (percent by volume of concrete) shall be not less than 5 percent or more than 7 percent." Every ready-mix supplier in this research sells 3,000 and 3,500 psi as standard stock, so the strength requirement costs you nothing and the air entrainment is the thing you have to ask for. That single sentence is the most useful thing on this page for anyone north of the freeze line.

And here is an open question we are not going to pretend to settle. No bagged concrete mix we could find publishes an air content. The data sheets give compressive strength and yield and say nothing about air, no ASTM C231 or C173 result, no freeze-thaw claim. So whether a pad built from bags satisfies that 5 to 7 percent requirement in a freeze-thaw climate cannot be determined from any manufacturer document. The whole DIY bag route for exterior pads in the northern US rests on it, and nobody publishes the answer.

The four pads people actually build

Air conditioner condenser pad. No code and no HVAC manufacturer specifies a size, thickness or strength. The only code line requires ground-supported equipment to sit on a slab "extending not less than 3 inches above the adjoining ground", which is a height, not a thickness. Bearing is a non-issue: a five ton condenser is about 26 pounds per square foot against the code's worst presumptive soil value of 1,500. The one useful manufacturer instruction is about noise rather than structure: the pad "should not be in contact with or be an integral part of the building foundation", because a compressor on a slab tied to your footing transmits hum into the house.

Generator pad. Manufacturers mostly accept gravel. One publishes a bed "approximately 5 in deep and approximately 3 in longer and wider than the generator", a level tolerance of half an inch, and an instruction not to remove the unit's own composite pad to bolt it to concrete. The one published sizing method for a concrete base is a commercial one, and it is a mass criterion rather than a bending one: base 12 inches larger on all sides, and depth such that the pad's own weight matches the machine's.

Hot tub or spa pad. The best-specified of the four, because the makers publish loads. Four converge on 4 inches of reinforced concrete, and two publish the load the pad must carry: 105 to 130 pounds per square foot, filled weights running from about 2,500 lb up to 5,810 lb, with one maker stating that the filled weight assumes an average occupant of 175 lb. One tells you to cross steel reinforcement bars throughout the pad. Note that 130 psf is under 9 percent of the worst soil the code recognizes, so this is a support-uniformity requirement rather than a bearing one, and the reinforcement is a warranty condition rather than a structural necessity. Full detail on a concrete slab for a hot tub.

Shed pad. The emptiest case. No code, standard or shed manufacturer source we could find specifies a pad for a shed, and a detached accessory building under the common 200 square foot permit exemption is usually outside the permitted scope entirely. See a concrete slab for a shed for what that means in practice.

One requirement nobody reports and it bites on AC and generator pads: the 2023 National Electrical Code added that the disconnecting means must meet the working space requirements of 110.26(A), which for a residential 240 V disconnect is 36 inches deep and 30 inches or the equipment width wide, measured from grade. That exceeds every manufacturer service clearance we found, so it is the number that sets where the pad goes.

Thickness, steel, and what you can skip

Four inches is convention rather than calculation, and the convention comes from the form board: a nominal 2x4 is 3-1/2 inches deep, which is also the IRC's minimum for a slab-on-ground floor. That provision is about a habitable floor inside the foundation walls, not an outdoor pad, so do not let it read as a requirement for one. Six inches is the usual call for a hot tub or anything a vehicle drives on.

On reinforcement, there is a clean sourced answer and it is no. ACI 330R states that distributed steel has "no significant effect on the load-carrying capacity or thickness" and is needed only where joint spacing exceeds 30 times the slab thickness. For a 4 inch pad that is 10 feet, so every pad smaller than 10 feet in any direction sits inside ACI's own no-reinforcement-needed window. Running ACI's subgrade drag equation for a 4 foot pad gives 0.005 square inches of steel per foot of width, which is about a sixth of what the lightest mesh sold provides. Rebar and wire mesh for a concrete slab covers the general case.

The exception is the hot tub, where the makers require it as a condition of the warranty. If you do use steel, position decides whether it does anything: it belongs in the upper third of the thickness, so about an inch and a quarter from the top on a 4 inch pad. Mesh walked down into the subgrade during the pour does nothing at all.

Mesh on a small pad costs far more than its headline rate, for the same reason the concrete does. The smallest sheet sold is 5 by 10 feet, 50 square feet, at $14.95. A 4 by 4 pad needs 16 square feet of it, so you pay 93 cents a square foot against a nominal 30, and two thirds of the sheet is waste. The short load logic turning up in a second line item.

Base, forms and the other line items

No code provision requires a base course under a freestanding exterior pad: the IRC's base and vapor retarder provisions both apply to slab-on-ground floors. Municipal standards that do spec a pad as a pad, for truck-loaded dumpster pads, call for 6 inches of compacted stone, which is an upper bound for a homeowner pad rather than a requirement.

If you do put stone down, the conversion that makes it calculable is a state DOT's own in-place factor of 1.85 tons per cubic yard:

Two cautions. The per-ton prices are bulk contracted rates on 500 to 457,000 tons; a 4 by 4 pad needs about 730 lb of stone, and no yard sells a third of a ton loose, so in practice that is the bagged gravel range and the small quantity penalty applies again. At 6 inches the forms have to be 2x6.

Notice the shape of the form row: form cost per square foot of pad falls eightfold from a 4 by 4 to a 30 by 40. That is the third independent appearance of the same effect on this page.

The line that sums the whole page up. On a 4 by 4 pad, the mesh sheet costs more than the forms and more than the gravel, and all three together cost less than the short load fee alone.

A vapor retarder is not required under an outdoor pad, by any code provision we could find, because the retarder exists to stop moisture reaching a floor covering in a conditioned space and there is no space above an equipment pad. Whether one is actively harmful out there, by trapping bleed water and aggravating curling, is a reasonable question that nobody appears to have published an answer to.

What a contractor charges, and the figure nobody publishes

Government wage data puts cement masons and concrete finishers at a median of $27.41 an hour. For scale on what a national average is worth: one state's prevailing wage determination for the same trade is $80.06 an hour fully loaded, 2.9 times that. The median also moved 18 percent in three years against 7.5 percent for ready-mix, so labor has inflated about two and a half times faster than the material.

One concrete contractor publishes a minimum job charge in dollars, on three of his own pages: 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." Two aggregators put a minimum at $500 to $900 and a contractor-software vendor's worked travel and setup example lands near $400, so the contractor-side figures are two to four times the aggregator-side ones. On a small pad that charge, not the concrete, is the largest line on the invoice. Concrete slab cost by size has the curve it produces. What is published comes from the supply side: a minimum charge of $162 to $810 by zone from one California supplier, a 2 yard minimum order from a Michigan one, and minimum orders of 3, 3 and 4 yards from three county bidders.

Public bid data shows the same effect at commercial scale, where mobilization is already paid for. One Wisconsin contractor priced 4 inch sidewalk at $4.65 a square foot on 18,450 square feet and $5.00 on 1,355. In a New Jersey contract the same bidder on the same day priced 4 inch sidewalk at $2.78 a square foot on 500 square yards and 6 inch sidewalk at $20.00 on 52 square yards, because a 52 yard item carries its own mobilization.

The unit price of concrete work is a function of the quantity, not a property of the material. A public agency buying 52 square yards pays seven times its own rate for 500. A homeowner buying 16 square feet is far below either.

Why the cost guides are wrong about small pads specifically

Seven consumer cost sources publish a price for a concrete pad or slab. Six of them never mention short load fees, supplier minimums or small pour premiums at all. We checked each page directly.

The seventh mentions it and is wrong by an order of magnitude. It states short loads cost "$15 to $17 per cubic yard". Against the published supplier charges in the first section, that understates the real short load fee by roughly 5 to 11 times, and understates a published per-load delivery charge by up to 35 times. The same page prices a one cubic yard delivery while stating elsewhere on itself that it is "incredibly hard to find a company that is willing to deliver a single yard".

Then there is the structural problem, checkable in a line of arithmetic. Every size table these sources publish scales perfectly linearly. One runs from 25 square feet to 1,600 at exactly $6.00 to $12.00 at both ends; another from 100 to 900 square feet at exactly $6.00; a third from 500 to 3,000 at exactly $5.00 to $37.00. Zero size effect across a 64-fold range of area.

Here is what that costs them. One source's smallest row is a 5 by 5 pad at $150 to $300 installed. That pad is 0.309 cubic yards. Priced at one Ohio supplier's published rates, billed at its 1 yard floor plus its 1 to 1.75 yard short load fee, the concrete alone is $338, which is about 13 percent above the published ceiling for the entire finished job. Against a California supplier it is $382, 27 percent above. Against every one of the seven suppliers in the first section, the ready-mix alone for a 5 by 5 pad costs more than that source says the finished pad costs.

The bag route is the only thing that rescues the number, and only just: 14 bags at $5.99 is $83.86, which does fit inside $150 to $300. But that is a DIY bag pour, which is not what a dollars-per-square-foot "installed" figure claims to describe.

Three more things before you average any of them. They are not seven sources: two publish an identical size table and an identical $6.00 a square foot and are owned by the same company, a third cites four of the others by name, and a fourth attributes its headline per-yard figure to a fifth publisher. They contradict themselves: one puts total installed cost at $4 to $8 a square foot on one page and labor alone at $8 to $18 on another, so its floor for labor equals its ceiling for the finished job; another publishes three different ranges across three live pages; a third publishes $6 to $9 in its body and $3 to $10 in its own FAQ. And only one discloses a sample size at all, 436 projects for a national average.

The sentence to take away: a price per square foot that scales linearly down to a 4 by 4 pad is not a cost estimate, it is a multiplication. Below about 3 cubic yards the bill is dominated by charges that do not scale with area at all.

Pad cost reference (US averages)

National averages as of 2025, used as the defaults in the calculator above.

Two notes on reconciling those defaults with the supplier documents above, because they are not in the same units and we would rather say so than let you trip over it. The calculator expresses the short load fee per cubic yard, which keeps the arithmetic simple, while every supplier we found publishes it as a flat charge per load of $90 to $175. To model a real quote, divide the per-load fee by the yards you are ordering and enter that. And the truck minimum field defaults to a conservative 10 yards, while the thresholds actually published run from 2 to 6; set it to your own supplier's figure before you trust the total.

Related tools: the concrete pad calculator for volume only, the slab cost calculator for a larger pour, the concrete cost calculator for ready-mix by the yard, and the concrete bag calculator if you are going the bagged route.