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Bag yields from the data sheets, strength from IRC Table R402.2

A cubic yard is 27 cubic feet and an 80 lb bag yields 0.60, so a yard is 45 bags and 3,600 lb of dry mix. That division is the whole of what most concrete calculators do. The code has a second question they never ask: IRC Table R402.2 sets a minimum compressive strength for what you are pouring, and in a freezing climate it also requires the mix to be air-entrained, which no amount of extra strength substitutes for.

Concrete volume, bags and strength

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Bag yields come from the manufacturer's data sheet, named in the table below. The strength figure is the model IRC cell, and your jurisdiction may have amended it.

Specification summary

Generated from on . Reopen that address to reproduce these figures exactly.

Entered

Result

This figure is drawn from the pour you type in above.
The pour, and the bags it would take

Concrete prices

Per sq ft installed unless stated
ItemLowHighUnit
Concrete slab$4$9per sq ft
Stained concrete$5$10per sq ft
Stamped concrete$5$10per sq ft
Polished concrete$3$8per sq ft
Painted concrete$2$6per sq ft
Aggregate concrete$2$3per sq ft
Whole concrete patio, all finishes$4$26per sq ft
Concrete removal$2$6per sq ft
Sealing$3$5per sq ft

Source: Lawn Love, how much does a concrete patio cost. Last price check: September 8, 2026.

A patio article, so the figures are for flatwork rather than footings or walls, and they are installed prices including labor rather than the cost of concrete alone. The article also quotes $125 per cubic yard for poured concrete as a materials figure.

Ready-mix concrete prices per yard

As each row states
ItemLowHighUnit
Ready-mix concrete, delivered and poured$119$147per cubic yard
Short load, under 10 cubic yards$53$53added per cubic yard
Saturday delivery$8$8added per cubic yard
Coloring$31$170added per cubic yard
Full 10 yard truckload$1,169$1,444total
Delivery past 20 miles$9.50$9.50per mile

Source: HomeGuide, how much does concrete cost per yard. Last price check: September 15, 2026.

The source's per-yard base covers delivery within 20 miles; a pour smaller than a full truck pays the short-load charge on every yard.

Worked example

A 10 ft by 12 ft patio slab at 4 in, one pour, 10% allowance, priced in Quikrete 80 lb bags, in a severe weathering area.

  1. Volume. 10 × 12 × 4/12 = 40 cu ft.
  2. Yards. 40 ÷ 27 = 1.48 cu yd. The 27 is a definition, not a measurement.
  3. Allowance. 10% on top is 44 cu ft, 1.63 cu yd, and ready-mix is sold in quarter yards so you order 1.75.
  4. Or in bags. 44 ÷ 0.60 = 74 bags, which is 5,920 lb of dry mix and 55 to 83 gallons of water.
  5. Strength. A patio is a porch or exterior slab. In a severe weathering area Table R402.2 wants 3,500 psi, and footnote d requires the concrete to be air-entrained at 5 to 7 percent.

Two things fall out of that. Seventy-four bags is not a wheelbarrow job, it is roughly six hours of mixing before you touch a float, and it is why the truck exists. And the 3,500 psi cell comes with an air requirement that bagged mix does not evidence: both data sheets on this page reach 4,000 psi at 28 days and neither one publishes an air content. Strength and air are separate requirements and only one of them is on the bag.

The formula

Volume, then two divisions, and neither division is the hard part:

V = L W t/12    yd³ = V(1 + k) / 27    bags = ⌈V(1 + k) / y⌉
L, W, t
slab length and width in ft, thickness in in. A footing is length × width/12 × depth/12; a round pier is πr² × depth
k
waste allowance. Ours, defaulting to 0.10, and nobody publishes one
27
cubic feet in a cubic yard. A definition
y
bag yield in cubic feet, from the data sheet. 0.60 for an 80 lb bag

Every Quikrete bag size works out at exactly 0.0075 cu ft per pound, so 27 ÷ 0.0075 = 3,600 lb of dry mix per cubic yard whatever size bag you buy. The only row in either manufacturer's range that breaks that rule is Sakrete's 90 lb bag, at 0.66 cu ft where the pattern says 0.675.

Why this page asks what you are pouring

Almost every concrete calculator takes three dimensions and returns cubic yards. That is arithmetic anybody can do, and it is genuinely most of what you need to place an order.

But the order has a second half. Ready-mix is specified, not just measured: you tell the supplier a strength and, in a freezing climate, an air content. IRC Table R402.2 is where those come from, and the cell you land in depends on whether the concrete is a basement slab, a foundation wall, a porch or a garage floor, and on the weathering potential where you live. A porch in a severe weathering area is 3,500 psi with 5 to 7 percent entrained air. A basement slab anywhere is 2,500 psi with no air requirement. Same truck, different ticket.

Air entrainment is the part that gets lost, because it is not a strength. It is deliberate microscopic voids that give freezing water somewhere to expand into, and without them a porch spalls its surface off in a few winters no matter how strong the concrete is. Footnote d is one sentence long and it decides whether your slab survives.

So this calculator asks two extra questions and prints the cell it landed in, with the footnote attached. It is still the model figure, and the last section on this page shows how far two real jurisdictions have moved it.

Bag yields as published, and what they mean per cubic yard
BagYield, cu ftCu ft per lbBags per cu ydlb of dry mix per cu ydMixing waterDocument
Quikrete 40 lb0.30.007590.03,6003 to 4 1/2 ptQuikrete data sheet 1101, CSI 03 31 00
Quikrete 50 lb0.3750.007572.03,6003 1/2 to 5 1/2 ptQuikrete data sheet 1101, CSI 03 31 00
Quikrete 60 lb0.450.007560.03,6004 to 7 ptQuikrete data sheet 1101, CSI 03 31 00
Quikrete 80 lb0.60.007545.03,6006 to 9 ptQuikrete data sheet 1101, CSI 03 31 00
Quikrete 90 lb0.6750.007540.03,6007 to 10 ptQuikrete data sheet 1101, CSI 03 31 00
Sakrete 40 lb0.30.007590.03,6001.75 qtSakrete TDS, Division 03 31 00, ©2023 (file dated January 2024)
Sakrete 60 lb0.450.007560.03,6002.5 qtSakrete TDS, Division 03 31 00, ©2023 (file dated January 2024)
Sakrete 80 lb0.60.007545.03,6003.5 qtSakrete TDS, Division 03 31 00, ©2023 (file dated January 2024)
Sakrete 90 lb0.660.0073340.93,6824.25 qtSakrete TDS, Division 03 31 00, ©2023 (file dated January 2024)

Read 2026-09-08. Columns three, four and five are derived from the published yield: cubic feet per pound, 27 divided by the yield, and that figure times the bag weight.

Download this table as CSV. Same cells as printed above, nothing added.

45 bags to the yard, and the one row the two brands disagree on

A cubic yard is 27 cubic feet. Every bag of concrete mix publishes its yield in cubic feet on the data sheet. So the bag count is one division, and the size of it is the point:

27 ÷ 0.60 = 45 bags of 80 lb per cubic yard

That is 3,600 lb of dry mix, twenty-three trips from the car, for one yard. A 10 by 10 ft slab at 4 in is 1.23 yd, so it is 56 bags. This is the arithmetic that decides whether you are mixing bags or booking a truck, and it is why the calculator prints both answers side by side rather than making the choice for you.

Quikrete's range is perfectly consistent. Every bag size, 40 through 90 lb, works out at exactly 0.0075 cubic feet per pound of dry mix. Not approximately: exactly, on all five sizes. Sakrete matches it at 40, 60 and 80 lb.

Then the 90 lb bag disagrees. Quikrete publishes 0.675 cu ft and Sakrete publishes 0.66, a difference of 2.2%. On the 0.0075 rule Sakrete's 90 lb bag should be 0.675. It is the only row in either range that breaks the pattern, so it is either a rounding decision or a genuinely different product, and neither sheet says which. Use the figure printed on the bag in front of you.

The half a concrete calculator never asks: what strength?

Cubic yards is the easy question. The code has a second one, and it is in IRC Table R402.2: a minimum specified compressive strength that depends on what you are pouring and on the weathering potential where you live.

IRC Table R402.2, as printed in the 2018 Seattle Residential Code. Minimum specified compressive strength, f'c, psi at 28 days
Type or location of concrete constructionNegligibleModerateSevere
Basement walls, foundations and other concrete not exposed to the weather2,5002,5002,500 c
Basement slabs and interior slabs on grade, except garage floor slabs2,5002,5002,500 c
Basement walls, foundation walls, exterior walls and other vertical concrete work exposed to the weather2,5003,000 d3,000 d
Porches, carport slabs and steps exposed to the weather, and garage floor slabs2,5003,000 d, e, f3,500 d, e, f
  • a. Strength at 28 days psi.
  • b. See Table R301.2(1) for weathering potential.
  • c. Concrete in these locations that is subject to freezing and thawing during construction shall be air-entrained concrete in accordance with Footnote d.
  • d. 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.
  • e. See Section R402.2 for maximum cementitious materials content.

Footnote d is the one that gets dropped. It is not about strength at all. In a moderate or severe weathering area the concrete must be air-entrained, 5 to 7 percent by volume, and that is a property of the mix you order, not something you can reach by buying a stronger bag. Water freezing inside cured concrete is what spalls a porch, and entrained air is the space it expands into.

Which is why a bagged mix hitting 4,000 psi at 28 days is not automatically compliant. Neither data sheet on this page publishes an air content at all. A cell that demands 5 to 7 percent entrained air cannot be answered by a document that is silent on air, and this page will not pretend it can.

Bags or a truck, and where the line actually is

The arithmetic decides this for you, and it decides it earlier than most people expect.

One cubic yard is 45 bags of 80 lb. That is 3,600 lb, roughly twenty-three trips from a car boot, and mixing it in a barrel mixer at a bag a minute with loading and cleaning is the better part of a working day. A 10 by 12 patio at 4 in, with an allowance, is 74 bags.

Ready-mix is sold in quarter-yard increments, which is why the ordered figure above rounds up to the next quarter rather than to nearest. Suppliers set a minimum load and charge a short-load fee below it, so a small pour costs more per yard than a large one, and that fee is usually still cheaper than seventy bags.

Bags win on three things: a pour a truck cannot reach, a pour too small to be worth a delivery, and a pour you want to do in stages. Post holes and pier footings are the classic case, and they are what the round pier option is for.

One thing bags do not do is a monolithic pour. A slab mixed in batches has cold joints wherever one batch stiffened before the next arrived, and a cold joint through the middle of a driveway is a crack that has already decided where it is going.

The waste allowance, and why the subgrade decides it

The 10% default here is ours. No manufacturer and no code publishes a figure, and the page would rather say that than dress a guess up as a standard.

What it is covering is not spillage. It is that a nominal 4 in slab is not 4 in anywhere except on paper. A subgrade graded by hand and a rake has hollows, and every hollow is filled with concrete you paid for. Over-excavation at the edges does the same. On a formed footing in firm ground the real overrun is small; on a slab over a rough subgrade it can beat 10% comfortably.

The direction of the error is not symmetrical, which is why the default is not zero. Running short mid-pour on a slab means the part already placed has begun to stiffen, and the joint where the second load meets it is a permanent line. Ordering a quarter yard too much means a wheelbarrow of leftovers.

Set it to zero and the calculator gives you the exact geometric volume, which is the right number to start from and the wrong number to order.

What this page does not do

It does not size anything structural. Footing width and depth, slab thickness and reinforcement are engineering questions that depend on soil bearing, frost depth and load, and frost depth in particular cannot be published as a single number because it is set locally.

It does not price anything. This site publishes no price of its own.

And it does not tell you your weathering potential. That is IRC Table R301.2(1), which is a map with jurisdiction-by-jurisdiction values, and reading it off a web page for your county is exactly the kind of guess this site refuses to make. Your building department has the answer and it takes one call.

Same table number, three jurisdictions, three answers

Table R402.2 is a model. What binds you is whatever your state or city adopted, and they move it in both directions:

  • Minnesota. Amends IRC Table R402.2 to ADD a Footings row at 5,000 psi under all three weathering potentials. The model table has no footings row at all. Footnote g permits 2,500 psi instead, with an approved admixture providing water and vapor resistance at least equivalent to 5,000 psi concrete. Minn. R. 1309.0402, published electronically 26 January 2015
  • Seattle. Five-sack 2,000 psi and five-and-a-half-sack 2,500 psi mixes per IBC Section 1904.2 are treated as equivalent to 3,000 psi for weathering potential, and air entrainment is not required to address weathering. 2018 Seattle Residential Code, Code Alternate R402.2, page 124

Read those two next to each other. A footing in Minnesota is specified at 5,000 psi, a figure that appears nowhere in the model table, which has no footings row at all. In Seattle a 2,000 psi five-sack mix counts as 3,000 for weathering and the air entrainment requirement is lifted. Same section number.

So the strength this calculator reports is the model figure, and it is a floor to start a conversation from, not an answer. Concrete goes under a house and stays there for fifty years. Ring the building department.

Where every figure on this page came from

Read 2026-09-08. Bag yields are from the manufacturer's own data sheet. The code table is transcribed from a government publication that prints it in full, and the two amendments are from the states' and cities' own rule documents.

DocumentRevisionWhat it establishes
QUIKRETE Concrete Mix, product no. 1101, technical data sheetQuikrete data sheet 1101, CSI 03 31 002,500 psi at 7 days, 4,000 psi at 28 days, ASTM C39. Unit weight approximately 140 lb/ft3, ASTM C138. Meets ASTM C387.
SAKRETE High-Strength Concrete Mix, technical data sheetSakrete TDS, Division 03 31 00, ©2023 (file dated January 2024)2,500 psi at 7 days, 4,000 psi at 28 days. Meets ASTM C387 and C39.
2018 Seattle Residential Code, Chapter 4 FoundationsSeattle Department of Construction and Inspections, page 124Carries the model IRC Table R402.2 in full, which is why it is the transcription source, plus a Seattle-only code alternate.
Minnesota Rules 1309.0402, Section R402, MaterialsOffice of the Revisor of Statutes, State of Minnesota, published electronically 26 January 2015A state amendment, not the model code. Quoted to show how far a jurisdiction can move the same cell.
Item 440, Reinforcement for Concrete, Table 1Texas Department of Transportation, 2024 Standard SpecificationsA state government publication reproducing the ASTM bar table in full, which is why it is the transcription source here rather than any of the calculator sites that reprint the same figures unsourced.
2015 Seattle Residential Code, Chapter 5 Floors, Section R506Seattle Department of Construction and Inspections, page 168Carries IRC Section R506 in full: minimum thickness, fill depth limits, the 4 in base course and its Group I exception, the vapor retarder and its four exceptions, and where reinforcement must sit.

Why the code table is quoted from Seattle rather than from the ICC. codes.iccsafe.org returns HTTP 403 and cannot be read from here. The 2018 Seattle Residential Code is a municipal government publication that reproduces IRC Table R402.2 in full, names its edition and its jurisdiction on the page, and marks its own amendments separately from the model text. That makes it checkable, which a paywalled document is not.

Frequently asked questions

How many bags of concrete are in a cubic yard?
Forty-five 80 lb bags, sixty 60 lb bags, or ninety 40 lb bags. A cubic yard is 27 cubic feet and an 80 lb bag of Quikrete Concrete Mix yields 0.60 cubic feet, so 27 divided by 0.60 is 45. Whichever size you buy it comes to the same 3,600 lb of dry mix, because every Quikrete bag size works out at exactly 0.0075 cubic feet per pound.
How much concrete do I need for a 10x12 slab?
At 4 in thick, 40 cubic feet, which is 1.48 cubic yards. With a 10% allowance for an uneven subgrade that is 1.63 cubic yards, and since ready-mix is sold in quarter-yard increments you would order 1.75. In bags it is 74 of the 80 lb size.
What strength concrete do I need for a patio?
IRC Table R402.2 puts porches, carport slabs, exterior steps and garage floor slabs at 2,500 psi where weathering potential is negligible, 3,000 psi where it is moderate and 3,500 psi where it is severe. In moderate and severe areas footnote d also requires the concrete to be air-entrained at 5 to 7 percent by volume. Check what your jurisdiction adopted, because the table is amended locally.
Is bagged concrete strong enough for a footing?
On strength alone, yes: both Quikrete Concrete Mix and Sakrete High-Strength Concrete Mix publish 4,000 psi at 28 days, above every cell in the model table. Air entrainment is a separate matter. Neither data sheet publishes an air content, so where footnote d applies a bagged mix does not evidence compliance. And Minnesota amends footings to 5,000 psi, which neither bag reaches.
What is air-entrained concrete and do I need it?
It is concrete with deliberate microscopic air voids, 5 to 7 percent by volume, that give freezing water somewhere to expand into. IRC Table R402.2 footnote d requires it for exterior walls, porches, steps and garage slabs in moderate and severe weathering areas. It is not a strength property, so you cannot substitute a stronger mix for it, and you have to ask for it when you order.
How much water does a bag of concrete need?
Quikrete gives 6 pints as a starting figure and 9 pints as the maximum expected for an 80 lb bag. Sakrete gives 3.5 quarts, which is 7 pints, for the same size. The water you add sets the water-cement ratio, which is why the maximum matters as much as the starting figure. Seventy-four bags is therefore somewhere between 55 and 83 gallons of water, which is worth knowing before you start rather than after.
Why do the two brands give different yields for a 90 lb bag?
Quikrete publishes 0.675 cubic feet and Sakrete publishes 0.66, a 2.2% difference. Every other bag size in both ranges is exactly 0.0075 cubic feet per pound, and Sakrete's 90 lb row is the only one in either range that breaks that pattern. Neither sheet explains it. Use the figure printed on the bag you are actually buying.
What is the difference between cement and concrete?
Cement is the powder that binds concrete. Concrete is cement mixed with sand, gravel and water, and a bag of concrete mix already contains all of them except the water. Nothing on this page is a cement calculator in the strict sense: the bag yields above are for complete concrete mix.
How do I convert square footage to concrete yardage?
Multiply the square footage by the thickness in inches, divide by 12 for cubic feet, then by 27 for cubic yards. At 4 in thick one cubic yard covers 81 square feet, so a 10 by 12 slab of 120 square feet is 1.48 yards before any allowance.
How much does concrete cost per cubic yard?
Lawn Love quotes $125 per cubic yard for poured concrete as a materials figure. Its installed slab price of $4 to $9 per square foot works out to $324 to $729 for the 81 square feet a yard covers at 4 in, because that price includes labor.
How much does a 12x12 concrete pad cost?
A 12x12 pad is 144 square feet, so at Lawn Love's installed slab price of $4 to $9 per square foot it is $576 to $1,296. At 4 in thick it is 48 cubic feet, or 1.78 cubic yards before any allowance, which is 80 bags of the 80 lb size. Those are the current figures on this page, last checked on September 8, 2026.
How much does a 24x24 concrete pad cost?
A 24x24 pad is 576 square feet, so the same $4 to $9 installed slab price puts it at $2,304 to $5,184. At 4 in thick it is 192 cubic feet, 7.11 cubic yards before any allowance, which is a truck rather than bags.
How much does concrete demolition cost?
Lawn Love prices concrete removal at $2 to $6 per square foot. To demo a 12x12 pad is therefore $288 to $864, and a 24x24 pad is $1,152 to $3,456. The source's removal row is per square foot of slab and names no thickness.
Does the concrete price include pumping?
None of the Lawn Love rows on this page prices a concrete pump, so this page has no figure for pumped concrete. A pump is hired where the truck cannot reach the pour, and it is a separate line from the concrete and the finish.
What is a design mix for concrete?
A design mix is a concrete proportioned to meet a specified performance, chiefly compressive strength at 28 days, rather than a fixed recipe. Where IRC Table R402.2 applies, the strength and the air content in its cell are what you ask the supplier's design mix to meet. This calculator gives volume and that cell; it does not proportion cement, sand, stone and water.
How much does concrete flatwork cost?
Lawn Love's December 2025 article gives $4 to $9 per square foot for a concrete slab, $5 to $10 for stamped and $5 to $10 for stained, with removal of old concrete at $2 to $6.
How much does a heated concrete floor cost?
HomeAdvisor's June 2026 guide averages radiant heat set in a concrete floor at $22.50 per square foot, and gives $6 to $20 per square foot for radiant floor heating generally.
How much do concrete countertops cost?
HomeAdvisor's June 2026 guide gives $50 to $150 per square foot for concrete countertops in its text, and its own material table gives $50 to $100.
How much does a concrete septic tank cost?
HomeAdvisor's June 2026 guide gives $900 to $1,500 for a 1,000 gallon tank and $1,500 to $2,500 for a 1,500 gallon tank, though it does not say whether those figures include installation. A whole conventional septic system installed is $3,000 to $8,000. A cement septic tank and a concrete septic tank are the same product.
How much does a truckload of concrete cost?
HomeGuide's January 2026 guide gives $1,169 to $1,444 for a full 10 cubic yard truckload of ready-mix, and $119 to $147 per cubic yard. A load under 10 yards adds $53 a yard, and Saturday delivery adds $8 a yard. Those are the current figures this site has, read in September 2026.
How much does it cost to lay or pour concrete per square foot?
Lawn Love's December 2025 article gives $4 to $9 per square foot for a poured concrete slab, laid and finished. A poured cement patio, a cement pad or a concrete backyard slab is priced the same way. A 12 by 12 ft pad is 144 sq ft, $576 to $1,296 at that rate, and a 10 by 20 ft patio is $800 to $1,800.
Is concrete cheaper than paving stones?
Usually, on published rates. Lawn Love's December 2025 article gives $4 to $9 per square foot for a plain concrete slab, and Lawn Love's December 2025 article gives $8 to $24 per square foot for a paver patio installed. Stamped concrete, at $5 to $10 in the same concrete article, closes most of the gap.
How much does it cost to stain or restain a concrete floor?
Lawn Love's December 2025 article gives $5 to $10 per square foot for stained concrete and $3 to $5 per square foot for sealing. A cement garage floor of 400 sq ft is $2,000 to $4,000 to stain at that rate. The article does not price restaining separately from a first stain.
How much do concrete roof tiles cost?
HomeAdvisor's June 2026 guide gives $9 to $18 per square foot for concrete roof tile installed and $2 to $4 for the tile alone, against $8 to $25 installed for clay.
How much does concrete board siding cost?
Concrete board siding is fiber cement. This Old House's April 2026 article gives $5 to $14 per square foot of wall installed, against $2.15 to $5.25 for vinyl, so fiber cement costs more than vinyl across most of both ranges.
What is the mix ratio for bagged concrete?
A bagged mix is already proportioned, so the only ratio you set is the water. Quikrete prints 6 to 9 pints of water for an 80 lb bag of its Concrete Mix, and Sakrete 3.5 quarts for its 80 lb High-Strength mix. More water than that raises the water-cement ratio and lowers the strength the bag is rated for.
How do I calculate the volume of a concrete column?
Area of the circle times the height: 3.1416 × radius² × height. A 12 in round column 8 ft tall is 3.1416 × 0.5² × 8 = 6.28 cu ft, which is 0.23 cu yd or about 10.5 bags of 80 lb mix at 0.6 cu ft a bag. A square column is width × depth × height.

Check these numbers yourself

How every figure here is verified: Sources & Method. Who builds this: , and the method is on About. Found something wrong? Tell us and it gets fixed or removed.

Figures on this page last checked against the source documents on 2026-09-08. Codes are amended locally; confirm against the edition your jurisdiction enforces.

Related calculators

Guides that use this calculator

More of them: all guides.

Ring your building department. The strength figures here are the model IRC Table R402.2 cells, read on 8 September 2026 from a government publication that prints the table in full. Jurisdictions amend that table in both directions, two documented examples are on this page, and weathering potential is set locally by IRC Table R301.2(1). Nothing here sizes a footing, a slab thickness or reinforcement.