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MaterialCalc — 20x40 Concrete Driveway Cost Calculator

Estimate prepared 09/02/2026. Estimates only; verify against your plans before ordering.

20x40 Concrete Driveway Cost Calculator

Five inches for cars, six if a truck uses it.

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Result

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20x40 is a two-car-wide driveway with room to walk around the doors — 800 square feet, and at 5 inches about 12 cubic yards. Width is the dimension people regret: ten feet is legal and miserable, twenty is what you actually want.

Assumptions used

These are the numbers behind the result. Where one of them is soft, the cost range widens rather than pretending to a precision the data does not have.

80 lb bag yield
0.6 ft³

Yield of one 80 lb bag of standard concrete mix.

Quikrete product data sheet — Published product data, checked 09/01/2026

60 lb bag yield
0.45 ft³

Yield of one 60 lb bag of standard concrete mix.

Quikrete product data sheet — Published product data, checked 09/01/2026

Ready-mix short-load threshold
1 yd³

Below roughly one cubic yard, most suppliers add a short-load fee that erases the price advantage over bags.

Regional ready-mix supplier schedules — Rough figure — widens the estimate range, checked 09/01/2026

Bags per pallet
42 bags

Above roughly one pallet of 80 lb bags, ready-mix is usually cheaper and always faster.

Home Depot / Lowe's pallet quantities — Industry standard, varies by supplier, checked 09/01/2026

Compacted gravel base under slab
4 in

Drains water away from the underside of the slab. Skipping it is the usual cause of a slab that heaves.

International Residential Code (2021) — Industry standard, varies by supplier, checked 09/01/2026

Crushed gravel density
105 lb/ft³

Compacted 3/4 in crushed stone. Varies by quarry and moisture; loose stone runs lighter.

USGS aggregate bulk density range — Industry standard, varies by supplier, checked 09/01/2026

Compaction allowance
0.2

Loose stone loses roughly a fifth of its volume once compacted, so order above the finished volume.

Standard earthwork practice — Rough figure — widens the estimate range, checked 09/01/2026

Vapor barrier roll coverage
1000 ft²

Home Depot / Lowe's published product data — Published product data, checked 09/01/2026

Welded wire mesh sheet coverage
150 ft²

One 5x10 ft sheet, less the overlap at the seams.

Home Depot / Lowe's published product data — Industry standard, varies by supplier, checked 09/01/2026

Prices verified 09/01/2026 (US national average, big-box retail shelf price and regional ready-mix quotes). Regional adjustment: Blended from RSMeans city cost index bands and BLS construction wage differentials.

The formula

800 ft² × thickness in feet ÷ 27 = cubic yards. At 5 in that is 800 × 0.4167 = 333 ft³ = 12.3 yd³ before waste. Base tonnage is the same footprint at the base depth, converted at 105 lb per cubic foot.

Worked examples

20x40 at 5 in

Length: 40 Width: 20 Thickness: 5 Waste: 10

About 13.6 cubic yards with waste and roughly 7 tons of base. Two trucks, or one large one if your supplier loads to 14.

20x40 at 6 in for truck traffic

Length: 40 Width: 20 Thickness: 6 Waste: 10

Just over 16 yards. If an RV, boat trailer or work truck parks here, this is the version to build.

12x40 single-width driveway at 5 in

Length: 40 Width: 12 Thickness: 5 Waste: 10

About 8.1 yards — 40% less concrete. Cheaper, and the version people wish they had made wider.

Choosing materials

  • Five inches under cars, six wherever a truck turns or parks. The apron by the street takes the worst of it — delivery trucks, garbage trucks and anything backing in.
  • Twenty feet of width fits two cars with doors that open. It is the single upgrade people say was worth it, and it costs about a third more concrete than a 15 ft driveway.
  • Control joints every 10 to 12 feet, and a joint wherever the width changes. Long driveways crack at their narrowest point unless you give them a joint there first.
  • Slope away from the garage, a quarter inch per foot minimum. Water running toward a garage door finds its way under the slab and, in freezing climates, lifts it.
  • The apron between the sidewalk and the street is usually the municipality's. It needs a permit, often has its own thickness spec, and is sometimes inspected separately.

Common questions

How much concrete for a 20x40 driveway?

At 5 inches thick, 12.3 cubic yards before waste and about 13.6 with a 10% allowance. At 6 inches it is 14.8 before waste. Order to the quarter yard and round up.

How wide should a driveway be?

Ten feet is the minimum for one car and is uncomfortably tight. Twelve is comfortable for one. Twenty fits two cars side by side with room to open the doors, which is what most people want and few build.

What does a 20x40 concrete driveway cost?

Material including base typically runs $3,000 to $4,600. Poured and finished by a contractor, roughly $4,800 to $9,600 — $6 to $12 per square foot. Removing an old driveway is extra.

How thick should a driveway be?

Five inches for passenger cars, six where a loaded pickup, RV or delivery truck uses it regularly. Four inches is common in older work and is why so many older driveways are cracked in the wheel tracks.

How much base under a driveway?

Four to six inches of compacted crushed stone — about 7 to 10 tons on a 20x40. On clay, go to six inches. The base matters more on a driveway than anywhere else because it spans more than one soil condition.

How long before I can drive on it?

Seven days for cars, 28 days for anything heavy, when the concrete reaches full design strength. Driving early does not crack it that day — it shortens the life in ways that show up years later.

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