How Much Does a Yard of Concrete Cover?

Coverage by thickness

A cubic yard is 27 cubic feet. To find how many square feet it covers, divide 27 by the thickness in feet, which is the same as dividing 324 by the thickness in inches. Here is that coverage chart done for every depth concrete gets poured at, with the figure most charts leave out: how many yards 100 square feet takes, which is the number you actually need when you are placing the order.

Most patios and walkways are poured at 4 inches, driveways at 4 to 6 inches, and footings deeper still. The thicker the pour, the less ground a single yard covers, and the relationship is exactly inverse: double the thickness and you halve the coverage. The 5 inch row is 64.8 square feet if you want it unrounded. The 3.5 inch row is there because a nominal 4 inch slab frequently is not 4 inches, which is the subject of the whole second half of this page. How thick a slab should be has the structural side, and concrete price per yard turns these quantities into money.

How far does a yard of concrete go?

Square feet is the honest answer, but it is rarely the one people picture. What they want to know is how much walk, drive or pad one yard actually gets them. That is the same 81 square feet divided by the width of whatever you are pouring.

Those widths are not arbitrary. In the public right of way the Access Board’s 2023 PROWAG final rule sets the continuous clear width of a pedestrian access route at "48 inches (1220 mm) minimum, exclusive of the width of any curb" in R302.2, and most municipalities build wider than that. On private property the 2010 ADA Standards drop to 36 inches. The sidewalk calculator carries both rules and sizes the pour against them. For driveways, published municipal figures run from 10 feet minimum to 24 feet maximum, with one state DOT calling 12 feet standard, which is where the two middle rows come from. The driveway calculator has the thickness defaults for vehicle loads.

The row that surprises people is the last one. A yard of concrete is about four feet of a two-car driveway. A 24 by 24 foot drive at 4 inches is a little over seven yards, which is most of a truckload, and that is before the apron thickens at the street.

Coverage for more than one yard

Coverage scales straight, so any quantity is just the one-yard figure multiplied out. This is the table to use when you are checking a quote rather than building one. The three fractional rows at the top are there because suppliers bill in quarter-yard increments, so a quote comes back as 4.25 or 7.75 yards rather than a round number, and because a partial yard is what you are working with if you are mixing bags. One thing those rows are not is an order you can place: ready-mix has a truck minimum, and a short load gets a surcharge rather than a smaller price.

The bottom row is the one worth remembering, because a full mixer is the natural ceiling on a single pour. Ten yards at 4 inches covers about 810 square feet, roughly a 28 by 29 foot slab. Anything bigger needs a second truck, and what a mixer actually holds matters more than the rated capacity, because loads average well under it. For the other direction, the square footage calculator takes an area and a thickness and returns the yards, and what a yard of concrete is covers the unit itself: its size, weight and the conversions.

How the units relate

People mix up cubic feet, cubic yards, and square feet, so here is the plain version.

• Cubic feet and cubic yards both measure volume, which is the actual amount of concrete. 27 cubic feet equals 1 cubic yard. Concrete is ordered in cubic yards.
• Square feet measures area, which is the flat surface you are covering. Square feet alone does not tell you how much concrete you need. You have to pair it with a thickness to get a volume.

That is the key idea: area plus thickness gives volume. A 100 square foot patio needs very different amounts of concrete at 4 inches versus 6 inches, even though the surface area is identical.

The metric version: how much a cubic meter of concrete covers

Everywhere except the United States, concrete is ordered in cubic meters and slabs are specified in millimeters, so the same question has a different arithmetic. It is also worth having because the two units are close enough to confuse and not close enough to substitute.

The conversion is exact in one direction only. An international yard has been exactly 0.9144 meters since the 1959 agreement, so a cubic yard is exactly 0.764554857984 cubic meters, and NIST publishes all twelve digits. Going back the other way does not terminate: a cubic meter is 1.307951 cubic yards, rounded. That ratio is the whole story. A cubic meter covers about 30.8 percent more ground than a cubic yard at the same thickness, because it is 30.8 percent more concrete.

Metric is tidier, and that is not a coincidence. A cubic meter at 100 mm covers exactly 10 square meters, and the cubic meters needed per 10 square meters is just the thickness in meters. The imperial version of the same relationship is 324 divided by the thickness in inches, which lands on a whole number only at 2, 3, 4, 6, 9 and 12 inches. There is nothing deep in that, it is only what happens when the volume unit and the length unit are powers of ten apart.

One trap worth naming, because the numbers are so close. Four inches is exactly 101.6 mm, so a 100 mm slab is slightly thinner than a 4 inch one and uses about 1.6 percent less concrete over the same area. Six inches is 152.4 mm against a 150 mm slab, the same 1.6 percent. On a small pad the difference disappears into the waste allowance. On a 2,000 square foot floor it is 24.69 cubic yards against 24.30, a difference of about 0.4 of a yard, which is more than a rounding error and less than a load. If you are reading a specification written in one system and ordering in the other, convert the thickness rather than assuming 100 mm and 4 inches are the same slab.

Working backward from your area

If you know the square footage you want to cover and the thickness, you can find the yards you need. Multiply the area by the thickness in feet, then divide by 27.

For a 300 square foot driveway at 4 inches:

• 300 x 0.33 = 99 cubic feet
• 99 ÷ 27 = 3.67 cubic yards

Those are plan quantities with nothing added, and ordering against them will leave you short for the reasons set out below. How much concrete do I need walks the formula through the measuring itself, and yardage by shape handles circles, footings and walls where a rectangle will not do.

The concrete yardage calculator runs all of this for you and adds a waste cushion, so you can go straight from your measurements to an order number without touching the arithmetic.

Why a yard never covers what the table says

Every figure above is arithmetic, and arithmetic assumes the ground is flat and the slab is exactly as thick as you specified. It never is. The standard that governs ready-mix concrete says so directly. ASTM C94, the specification every ready-mix supplier sells under, carries a note under its basis of purchase clause warning that "the volume of hardened concrete may be, or appear to be, less than expected due to waste and spillage, over-excavation, spreading forms, some loss of entrained air, or settlement of wet mixtures, none of which are the responsibility of the producer." That is a standards body telling you, inside the specification itself, that the yard you buy is not the yard you end up with.

It matters where the yard is measured. C94 sets the basis of purchase as a cubic yard of fresh concrete as discharged from the truck, and the volume is not measured at all. It is calculated: total batch mass divided by the measured density of the fresh concrete, tested under ASTM C138. So a short-load dispute is settled with a density test on three trucks, not by measuring your slab.

The subgrade is where the concrete goes

ACI 117, the tolerance standard for concrete construction, allows the fine grade under a slab on ground to deviate by plus or minus three quarters of an inch. That is a legal, in-specification subgrade. On a nominal 4 inch slab, three quarters of an inch low is nearly 20 percent more concrete than the plan says, and nobody has done anything wrong.

The tolerance on slab thickness itself is one-sided. ACI 117 allows the average of the samples to run three eighths of an inch thin, and any individual sample three quarters of an inch thin. There is no plus tolerance at all. The standard caps how thin a slab may be and says nothing about how thick, which means the extra depth you pay for is never out of spec.

The arithmetic on that is simple, and worth committing to memory: every one eighth of an inch the grade runs low costs about 0.39 cubic yards per 1,000 square feet. Check it: 1,000 sq ft at 0.125 ÷ 12 ft deep is 10.42 cubic feet, which is 0.39 cubic yards. A quarter inch low across a 1,000 square foot pour is three quarters of a yard of concrete you did not plan for.

NRMCA works the same example from the other direction: an eighth of an inch on a 4 inch slab is roughly a 3 percent shortage, which on a 32 yard order leaves you about one yard short.

Concrete also shrinks between the truck and the finished slab

The same NRMCA bulletin puts the hardened volume at about 2 percent less than the fresh volume, from air loss, bleeding and settlement, reduction in the paste volume, and drying shrinkage. So even a perfectly graded subgrade returns slightly less finished slab than the delivery ticket says.

On top of that sits normal batch variation. ASTM C94 sets no tolerance on yield itself, only on the ingredients: cement within 1 percent, aggregate within 2 percent, water within 3 percent. NRMCA converts that into a real-world yield band of about 1 percent for non-air-entrained concrete, 2 percent for air-entrained, and up to 3 percent at high air contents. Worth knowing if you ever suspect a short load: an under-yielding batch is a richer mix, not a cheated one, because the same cement ends up in less concrete.

So how much extra should you order?

The number the industry publishes is 4 to 10 percent above the plan quantity. NRMCA's ordering bulletin puts it this way: order 4 to 10 percent more than the plan estimate "to account for contingencies such as waste, over-excavation, spreading of forms, etc." Its companion bulletin on yield gives the same range independently.

Two things are worth noticing about that. It starts at 4 percent, not 10, which is lower than the flat "always add 10 percent" you see repeated everywhere. And it is the only published number of its kind. There is no standards body figure for how much a yard actually covers in practice versus theory: ASTM names the causes without quantifying them, NRMCA quantifies the individual causes, and the 4 to 10 percent allowance is the industry's stand-in for an answer nobody has measured.

Where to sit inside that range depends on the pour. A formed footing on firm ground with a screeded base is near the bottom. A slab on a hand-graded subgrade, a pour against soil, or anything where the forms can spread belongs near the top. Slab thickness and how well the base is compacted move the number more than anything else on the job.

Coverage per bag, for small pours

Bagged concrete works the same way, one bag at a time. Quikrete and Sakrete both publish the yield of every bag size on their data sheets, and the two brands agree on everything but the 90 lb bag.

Sources: Quikrete Concrete Mix no. 1101 and the Sakrete High-Strength Concrete Mix data sheet. Sakrete does not make a 50 lb concrete mix bag, so that row is Quikrete only.

Look closely at those yields and you can see what they are. Multiply each one out: 0.30 by 90 is 27.0, 0.45 by 60 is 27.0, 0.60 by 45 is 27.0. Every published bag yield is an exact divisor of 27 cubic feet, and every data sheet says "approximately." These are design values, not tested ones. They are internally sound, since 80 lb of dry mix plus about 3.5 quarts of water over 0.60 cubic feet works out to roughly 145 lb per cubic foot, which is normal weight concrete. But they carry the same caveat as everything else on this page: treat them as a starting point and buy a spare bag.

To go from an area straight to a bag count, the concrete bag calculator does it by bag size, and bags per yard has the full chart if you are comparing bags against a ready-mix order.