How many cubic yards is a 10 x 10 slab at 4 inches?

1.23 cubic yards. 10 x 10 = 100 sq ft, times 4 / 12 = 33.3 cu ft, divided by 27 = 1.23 cu yd before any over-order.

How many square feet does a cubic yard of concrete cover?

It depends on thickness: 27 divided by the thickness in feet. That is 81 sq ft at 4 in, 64.8 sq ft at 5 in and 54 sq ft at 6 in.

How much extra concrete should I order?

Allow 5 to 10 percent over the calculated volume. The calculator defaults to 10 percent; change it to suit the job.

Does it count bags of concrete?

No. Bag yields vary by product and bag size, so read the yield on the bag and divide the cubic feet by it. For anything bigger than a small pad, price ready-mix by the cubic yard.

Is this number a quote?

No. It is an estimate to help you plan and build your bid. Confirm the final quantity with your supplier before you order.

Free calculator

Concrete calculator (cubic yards)

Multiply length by width in feet, multiply by the thickness in inches divided by 12, then divide by 27. A 10 x 10 ft slab at 4 in is 1.23 cubic yards; a 20 x 24 ft slab at 4 in is 5.93.

Your job

Slab size

Length

Width

Thickness

4 in is typical for residential slabs, patios, sidewalks and driveways; 5 to 6 in for heavier vehicles.

Over-order

Over-order allowance10%

5 to 10 percent is the usual allowance over the calculated volume.

Plan view to scale, with the slab thickness in section below.

Concrete to order

6.52cu yd

5.93 cu yd plus 10 percent

In the slab

5.93cu yd

Before over-order

Volume

160.0cu ft

Slab area

480sq ft

One cu yd covers

81.0sq ft

At 4.00 in thick

The working, with your numbers

1. Area24.00 x 20.00= 480.0 sq ft
2. Thickness4.00 / 12= 0.333 ft
3. Volume480.0 x 0.333= 160.0 cu ft
4. Cubic yards160.0 / 27= 5.93 cu yd
5. To order5.93 x 1.10= 6.52 cu yd

Typed those measurements in by hand?MetreMate measures them straight off your PDF plans. Free to start.

The formula, in plain words

1Slab area in square feet = length in feet times width in feet.
2Thickness in feet = thickness in inches divided by 12.
3Volume in cubic feet = area times thickness in feet.
4Cubic yards = cubic feet divided by 27 (one cubic yard is 3 x 3 x 3 ft).
5Cubic yards to order = cubic yards times (1 plus your over-order allowance).

Worked example

A 20 x 24 ft slab poured 4 in thick, with a 10 percent over-order allowance.

1.Area: 20 x 24 = 480 sq ft.
2.Thickness: 4 / 12 = 0.333 ft.
3.Volume: 480 x 0.333 = 160 cu ft.
4.Cubic yards: 160 / 27 = 5.93 cu yd.
5.With 10 percent over: 5.93 x 1.10 = 6.52 cu yd.

Answer: 5.93 cu yd in the slab, about 6.52 cu yd to order with 10 percent over.

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How to measure it

Take the slab length and width in feet off the plan or the site. For an irregular slab, measure its area in square feet and use the area option.
Thickness comes from the drawings or the spec, in inches. Residential slabs, patios, sidewalks and driveways are typically 4 in.
Thickened edges, footings and piers are extra volume. Work them out separately and add them.

Where the numbers come from

Every default in the calculator comes from a published source. We list the source next to it so you can check.

What	Value	Source
One cubic yard (3 x 3 x 3 ft); slab cu yd = sq ft x (thickness in / 12) / 27	27 cu ft per cu yd	Concrete Network, how much concrete for a driveway (checked 2026-09-20)
Typical thickness for residential slabs, patios, sidewalks and driveways (5 to 6 in for heavier vehicles)	4 in	Concrete Network, how much concrete for a driveway (checked 2026-09-20)
Over-order allowance, 5 to 10 percent (we default to the top of the range)	10 percent	ConcreteCalcs, how to calculate concrete for slabs (checked 2026-09-20)
Inches in one foot (the foot is exactly 12 inches)	12 in per ft	Wikipedia, Foot (unit) (checked 2026-10-01)

Manufacturers named here are the source of the number, not a recommendation. Confirm quantities with your supplier.

Frequently asked questions

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