Concrete Driveway Calculator: Volume and Thickness

Concrete driveway volume formula

V = length × width × thickness

Multiply the driveway's length by its width to get the area, then by the thickness — all in the same unit. Convert the result to cubic yards or cubic metres to order, and add 10% for waste, uneven subgrade and spillage.

Worked example: A 30 ft × 10 ft driveway at 4 in thick is 300 × 0.333 = 100 ft³, which is 3.7 cubic yards, so order about 4.1 with the buffer.

A driveway is the largest slab most homes will ever have poured, and the one where a short order hurts most — a cold joint across a driveway is permanent and visible. The volume itself is simple length × width × thickness. The decisions that matter are the thickness and what goes underneath.

Concrete for common driveway sizes

Driveway	Size	Thickness	Concrete
Single, short	10 × 20 ft	4 in	2.5 yd³
Single, long	10 × 30 ft	4 in	3.7 yd³
Double	20 × 20 ft	4 in	4.9 yd³
Double, long	20 × 30 ft	5 in	9.3 yd³
Double, heavy duty	24 × 24 ft	6 in	10.7 yd³

In metric:

Driveway	Size	Thickness	Concrete
Single, short	3 × 6 m	100 mm	1.8 m³
Single, long	3 × 9 m	100 mm	2.7 m³
Double	6 × 6 m	100 mm	3.6 m³
Double, long	6 × 9 m	125 mm	6.8 m³
Double, heavy duty	7.2 × 7.2 m	150 mm	7.8 m³

These are the raw volumes. Add the 10% buffer before ordering.

Choosing the thickness

100 mm (4 in) — cars, light utes, ordinary domestic traffic. The default.
125 mm (5 in) — a caravan, boat trailer or a heavier vehicle parked regularly.
150 mm (6 in) — RVs, delivery trucks, tradesmen’s trucks, or anywhere heavy vehicles turn rather than drive straight through.

Turning is what breaks driveways. A truck driving over a slab loads it far less than the same truck turning its wheels on the spot, which grinds and twists the surface. If a bin lorry or delivery truck swings across your driveway, build for it.

The extra concrete is cheap relative to the job. Going from 100 mm to 125 mm on a 6 × 6 m driveway is under a cubic metre — a fraction of the cost of breaking out and re-pouring a failed slab.

What goes underneath matters more than the mix

Driveways rarely fail because the concrete was weak. They fail because what was underneath moved.

Compact the subgrade. Strip topsoil and organic material completely — it will rot and settle. Compact in layers.
Lay 100-150 mm of granular subbase and compact it too. It spreads load and, just as importantly, drains water away from beneath the slab.
Reinforce. Mesh or rebar will not prevent cracks. It holds them closed so the slab keeps acting as one piece. Support it on chairs in the middle third of the depth — mesh lying on the subgrade contributes nothing.
Set the fall before you pour. A minimum of 1%, ideally 2%, away from the house. This is formwork, not finishing; you cannot fix it later.

Control joints

Concrete will crack. Control joints decide where. Space them at roughly two to three times the slab thickness measured in feet — about 3 m for a 100 mm slab — and cut or tool them within 24 hours of the pour, at least a quarter of the slab depth. Keep the panels close to square: a long, narrow panel will crack across its middle regardless of the joints at its ends.

Ordering and pour day

At two cubic metres and up, this is a ready-mix job — bagged concrete stops making sense somewhere around one cubic metre, and a driveway needs to go down continuously anyway.

Check truck access. A loaded truck is around 30 tonnes. Verges, service covers and septic tanks do not always survive one.
Have the crew ready before the truck. A driveway has to be placed, screeded and finished in one continuous operation. Trucks charge waiting time and concrete does not wait at all.
Watch the weather. Do not pour into standing water, or within a few hours of heavy rain or hard frost. Hot, windy days are just as risky — the surface skins over before you can finish it.

Use it on the jobsite

The Concrete Calculator app for iOS has this same calculator plus saved projects, history, four more calculator types and full offline support. Get it on the App Store.

Pouring a different shape? The rectangular slab calculator is the same tool with general-purpose defaults, and the slab area calculator handles driveways that are not a simple rectangle — an L-shape around a corner, or one that widens into a parking bay.

Frequently asked questions

How thick should a concrete driveway be?

100 mm (4 in) is the standard for cars and light utes. Go to 125-150 mm (5-6 in) if a caravan, boat trailer, RV or delivery truck will use it, and 150 mm where heavy vehicles turn. The extra 25 mm on a typical driveway costs roughly a quarter more concrete and is far cheaper than replacing a cracked slab.

How much concrete does a two-car driveway need?

A 6 m × 6 m (20 ft × 20 ft) driveway at 100 mm is 3.6 m³, or about 4.9 cubic yards. At 125 mm the same area needs 4.5 m³. Order to the buffered figure — a short pour means a cold joint across the driveway.

Does a driveway need reinforcement?

Most do. Steel mesh or rebar does not stop concrete cracking, but it holds the crack tight so the slab keeps working as one piece and the edges don't step apart. Place it in the middle third of the slab depth on chairs, not thrown on the subgrade where it does nothing.

How far apart should control joints be?

Roughly two to three times the slab thickness in feet — so about 3 m (10 ft) for a 100 mm slab and 3.5-4 m for 150 mm. Cut or tool them within 24 hours, at least a quarter of the slab depth. Keep panels close to square; long thin panels crack across the middle.

What fall does a driveway need for drainage?

A minimum of 1% and ideally 2% — 20 mm per metre — running away from the house. Set the formwork to that fall before you pour; you cannot correct drainage after the concrete is down, and water pooling against a building is a far more expensive problem than a slightly steeper driveway.

Do I need a subbase under the driveway?

Yes. 100-150 mm of compacted granular fill spreads the load, drains water from under the slab and gives a uniform surface to pour on. Concrete poured straight onto soft or uneven ground settles unevenly, and that is what cracks driveways.

Concrete Driveway Calculator: Volume and Thickness

Calculator

Concrete required

Concrete driveway volume formula

Concrete for common driveway sizes

Choosing the thickness

What goes underneath matters more than the mix

Control joints

Ordering and pour day

Use it on the jobsite

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Frequently asked questions