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How Many Square Feet Does a Yard of Concrete Cover?

You have a slab area and a thickness. The plant wants cubic yards.

Short answer

One cubic yard of concrete covers 81 square feet at 4 inches thick, 65 square feet at 5 inches, and 54 square feet at 6 inches. The shortcut is 324 ÷ thickness in inches, because a cubic yard spread one inch deep covers 324 square feet.

Run it on your own numbers

Concrete needed
2.72 yd³
Cost
$500 – $800

Measure these

For a round column this is the diameter.

4 in residential slab, 5–6 in driveway, 6 in+ for heavy vehicles.

Sensible defaults are already applied — open only if you need to change them.

4″20′10′VOLUME · LENGTH × WIDTH × DEPTH
Concrete needed
2.72 yd³
2.47 yd³ measured + 10% · 66.7 ft³
Material cost
$500 – $800
Bags of 80 lb
123

each yields 0.6 ft³ · 2.73 yd³ equivalent

Order this much
2.75 yd³

Plants sell in quarter-yard increments

Placed weight
5.5 tons

≈ 4,050 lb per yd³

Bagged cost
$800

123 bags — compare against the truck price below

Ready-mix $140–200/yd³ plus short-load fee, or bags at retail. The lower of the two is shown as the floor.

At 2.72 yd³ you are a short load. Plants charge a surcharge under 8–10 yd³ — usually $100–200 — so budget for it and ask what their minimum is before you book.

123 bags is roughly 2.7 yards mixed by hand. Past about half a yard a truck is cheaper and vastly faster — and hand-mixing a slab in batches risks a cold joint through the middle of it.

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Coverage by slab thickness

ThicknessSq ft per yd³Yd³ per 100 sq ftTypical use
2 in1620.62Overlay, topping
3 in1080.93Light path
4 incommon811.24Patio, sidewalk, shed pad
5 in651.54Driveway
6 in541.85Garage, heavy vehicles
8 in40.52.47Commercial, equipment pads
12 in273.70Footings, piers

Every figure here is 324 ÷ thickness in inches. That single number handles any depth you are asked about.

Where the 324 comes from

A cubic yard is 27 cubic feet. Spread one inch deep — that is 1/12 of a foot — it covers 27 ÷ (1/12) = 324 square feet. Every other coverage figure is that number divided by the thickness in inches.

Worked example: a 24 × 24 ft garage slab at 5 inches is 576 square feet. 576 ÷ 65 = 8.9 cubic yards. Add 10% overage and you order 9.75 yards, which is close enough to a full truck to avoid a short-load fee.

Reverse example: you have 6 yards booked and want a 4-inch patio. 6 × 81 = 486 square feet, so about 22 × 22 ft.

Choosing the thickness

Four inches is the residential minimum for anything walked on — patios, sidewalks, shed pads. Below 4 inches concrete cracks along its shrinkage lines no matter how good the mix is.

Driveways want 5 inches, and 6 if a truck or an RV ever parks on it. The extra inch on a 20 × 24 ft driveway is about 1.5 cubic yards, roughly $250 of concrete — considerably cheaper than replacing a cracked slab.

Thickness is not a substitute for a proper base. Four inches of compacted crusher run under a slab does more for its life than an extra inch of concrete over soft ground, because the failure mode is the subgrade moving, not the concrete being weak.

Frequently asked questions

How many square feet does a yard of concrete cover at 4 inches?

81 square feet. At 5 inches it is 65, and at 6 inches, 54.

How do I work out coverage for any thickness?

Divide 324 by the thickness in inches. A cubic yard spread one inch deep covers 324 square feet.

How many yards of concrete for a 20x20 slab?

400 square feet at 4 inches is 4.94 cubic yards, so about 5.5 yards with overage. At 6 inches it is 7.4 yards, or 8.2 with overage.

How thick should a concrete driveway be?

Five inches for cars, six for trucks or RVs, over a compacted base of at least 4 inches. Four inches is patio thickness and will crack under vehicle loads.