Concrete Driveway Calculator

How do you calculate concrete for a driveway?

A driveway is a long, flat slab, so its volume is length × width × thickness. Measure length and width in feet, thickness in inches, and use this formula to go straight to cubic yards, the unit ready-mix plants sell:

Cubic yards = length (ft) × width (ft) × thickness (in) ÷ 324

The 324 is 12 inches per foot × 27 cubic feet per cubic yard. For metric, multiply length × width in metres by thickness in metres: a driveway 12 m × 3.6 m at 12.5 cm is 5.4 m³.

1. Measure inside the forms. Measure the apron at the street, flares and any wider parking area as separate shapes.
2. Check the base depth in several places. A low spot in the gravel becomes extra concrete.
3. Enter each shape in the calculator above and use Add to project to total them. It returns cubic yards, cubic feet, m³, bag counts and weight.
4. Add 10% for spillage and an uneven base, then round up to the next ¼ yd³.

How much concrete for common driveway sizes?

The table gives exact cubic yards for typical driveway sizes at 4, 5 and 6 in thick, plus the order at 5 in with 10% extra rounded up to the next ¼ yard. Every figure comes from the same calculation the tool uses.

Two driveways with the same area need the same concrete whatever their shape: 12 × 80 ft and 24 × 40 ft are both 960 ft² and 14.81 yd³ at 5 in.

By square footage

If you already know the area, for example from a site plan or a quote, use these figures. Each row is the exact volume; the last column is the order at 5 in with 10% extra.

To convert any other area, use the square feet to cubic yards converter.

How thick should a concrete driveway be?

Thickness drives both volume and cost. Your local code, permit or engineer sets the required thickness, so confirm it before you price the job. Each extra inch adds 0.31 yd³ per 100 ft², which is 1.48 yd³ on a 12 × 40 ft driveway.

These figures show volume and weight only; they are not a thickness recommendation. Many towns set their own rules for driveway thickness, the apron at the street and reinforcement, and some require a permit. Ask your building department before you order. Thicker concrete does not fix a poor base; compaction matters as much as depth.

A practical approach: find out the thickness your local rules require, and if a pickup with a loaded trailer, an RV, a boat or delivery trucks will use the driveway, ask your building department or an engineer whether it should be thicker, then price each option in the calculator. Going from 4 to 5 in adds 25% to the concrete; from 4 to 6 in adds 50%.

Single-car vs two-car driveways

Width matters as much as length. Many single-lane driveways are 10–12 ft wide and many two-car driveways are 16–20 ft wide or more; measure yours, because the order scales directly with width. On a 40 ft run at 5 in, every extra foot of width adds 0.62 yd³.

• 12 ft single lane, 40 ft long: 7.41 yd³ at 5 in, order 8¼ yd³.
• 20 ft two-car, 40 ft long: 12.35 yd³ at 5 in, order 13¾ yd³.
• 24 ft two-car, 40 ft long: 14.81 yd³ at 5 in, order 16½ yd³.

A single lane that widens to a two-car pad in front of the garage is best measured as two rectangles. That is what the next example does.

Aprons, flares, parking pads and thickened edges

The main rectangle is rarely the whole job. Calculate these separately and use Add to project to total them:

• Street apron. Many cities require a thicker apron. A 12 × 6 ft apron at 6 in adds 1.33 yd³; a 16 × 6 ft apron adds 1.78 yd³; a 20 × 8 ft apron adds 2.96 yd³.
• Flares at the street. A flare is roughly a triangle: half of length × width. Two triangular flares with 4 ft legs at 5 in add 6.67 ft³ (0.25 yd³).
• Parking pad or turnaround. A 10 × 20 ft pad at 5 in adds 3.09 yd³.
• Thickened edges. A turned-down edge along both sides of a 40 ft driveway, 12 in wide and 5 in deeper than the slab, adds 1.23 yd³. Size it like a footing with the footing calculator.

Metric driveway volumes

In metric countries ready-mix is ordered in cubic metres, and the maths is length × width × thickness, all in metres.

Switch the calculator to Metric and enter metres and centimetres; it shows m³ alongside cubic yards. Round up to your supplier’s increment.

Curved and sloped driveways

Curved driveways. Measure the length along the centre line of the curve, then multiply by the average width. A driveway that curves for 60 ft along its centre line and is 12 ft wide is treated as 12 × 60 ft: 8.89 yd³ at 4 in or 11.11 yd³ at 5 in. If the width changes, split it into sections and average each one. Measuring along the outside edge of the curve overstates the volume; the inside edge understates it.

Sloped driveways. Measure the length along the surface, not on the plan. On most residential slopes the difference is small: a driveway 40 ft long on the plan that climbs 4 ft is 40.2 ft along the surface, about 0.5% more concrete. Steep driveways change other things more than the volume, such as the concrete’s slump, the finish and how the truck discharges, so tell the plant about the slope when you order.

Small repairs and patches

For a patch, calculate only the section you are cutting out. A 4 × 6 ft section of a 4 in driveway is 8 ft³, which is 14 bags of 80 lb concrete, or 15 with 10% extra. A 3 × 5 ft section is 5 ft³: 9 bags, or 10 with extra. Patches this size are a bag job; mix one batch at a time and keep the first bags covered until the area is ready.

Match the new thickness to the old slab by measuring the cut edge, not by assuming 4 in. Older driveways are often thinner or thicker than you expect, and a patch that is 1 in thinner than the slab around it is a weak spot.

Ready-mix or bags for a driveway?

Ready-mix, almost always. Even a small 10 × 20 ft driveway at 4 in is 2.47 yd³, which is 112 bags of 80 lb concrete and about 9,000 lb of dry mix to lift and mix. A driveway also needs to be placed and finished in one continuous pour, and hand mixing that much risks cold joints, weak seams where fresh concrete meets concrete that has started to set.

• Bags make sense for repairs, a small apron patch or a pad under about ½ yd³ (around 23 × 80 lb bags). QUIKRETE lists driveway repairs among the uses of its Concrete Mix.
• Ready-mix is sold by the cubic yard. Ask the plant about its order increment, any minimum-load or short-load charge, and how much one truck carries so you can plan a second load on long driveways.
• Get two or three quotes with your exact yardage and thickness. Our driveway cost guide explains what drives the price, and the calculator takes your own price per yard.

Planning the pour on a long driveway

Once the order is above one truckload, the schedule matters as much as the volume. Ask the plant how many yards each truck carries on your street, then divide your order by that figure and round up to get the number of loads. Tell the dispatcher the gap you need between trucks so the crew can place and screed each load before the next arrives.

• Pour from the far end toward the street, so trucks and wheelbarrows never cross fresh concrete.
• Hold the last few yards back. Order the final truck once the first loads are placed and you can see how much is left; the plant can adjust it.
• Plan control joints before the pour. Mark where they go on the forms so the finisher can cut or tool them on time. Your plans or the contractor set the spacing.
• Keep the base wet but not puddled on a hot day so it does not pull water from the concrete.

Replacing an old driveway

A replacement starts with demolition. Cured concrete weighs about 2 tons per cubic yard (150 lb/ft³ × 27 ft³ = 4,050 lb), slightly more if it is reinforced (WSDOT uses 155 lb/ft³), so an old driveway is heavy debris: a 40 × 12 ft driveway 4 in thick is 5.93 yd³ in place, roughly 12 tons to haul away. A 50 × 12 ft driveway at 5 in is about 18.8 tons. Ask the hauler or recycler about container size and weight limits before you book.

Some yards crush old concrete into aggregate. If you are building a crushed concrete driveway instead of pouring a new slab, calculate it like gravel: length × width × depth gives cubic yards, then add 10–20% for compaction and convert to tons with the supplier’s figure. The crushed concrete calculator converts it to tons with FHWA’s measured density, and the driveway gravel calculator handles layered bases.

Prepare the base before you order

A firm, even base is what keeps a driveway from cracking and keeps your order accurate.

• Strip topsoil and soft material down to firm subgrade.
• Place and compact a gravel base in layers. The driveway gravel calculator gives tons for the base.
• Set forms with a fall away from the garage and house so water drains.
• Add rebar or wire mesh where your plans call for it. The rebar calculator sizes a grid.
• Re-measure depth from a string line across the forms just before the truck arrives, and update the calculator if the base has moved.

Common mistakes when estimating a concrete driveway

1. Forgetting the apron and flares. A 12 × 6 ft apron at 6 in is 1.33 yd³ on its own, more than a full yard you would not have ordered.
2. Using the planned thickness for a base that is low. A base ½ in low across a 12 × 40 ft driveway adds 0.74 yd³; 1 in low adds 1.48 yd³.
3. Measuring the outside of the forms. If your forms are 2× lumber (1½ in thick), the outside measurement is 3 in wider than the slab, and that error runs the full length. Measure between the inside faces of the forms.
4. Ordering exactly to the yard. A 40 × 12 ft driveway at 5 in is 7.41 yd³; ordering 7½ yd³ leaves 0.09 yd³ of margin. Add 10% and order 8¼ yd³.
5. Choosing thickness by habit. Going from 4 to 6 in on a 20 × 40 ft driveway adds 4.94 yd³. Match the thickness to the vehicles and your local rules, then price it.
6. Forgetting the weight of the old slab. Ripping out a 40 × 12 ft driveway is about 12 tons of debris, which changes the hauling plan and the budget.

Driveway calculator vs other calculators: which one to use

• This driveway calculator: a new poured concrete driveway, its apron, flares and parking pads.
• Concrete slab calculator: patios, shed bases, garage floors and other flat pads, including round slabs and monolithic slabs.
• Concrete driveway cost: turning the yardage into a budget with your own price per yard, labor and extras.
• Driveway gravel calculator: the gravel base under the concrete, or a gravel or crushed concrete driveway instead of a poured one.
• Rebar calculator: bar counts and lengths for a reinforcement grid.