Concrete Coverage Calculator

1. Choose what to find: the area a given amount covers, or the thickness it pours over a known area.
2. Enter the amount of concrete and pick its unit: cubic yards, cubic feet or bags.
3. Enter the thickness in inches for area mode, or the area in square feet for thickness mode.
4. Set a waste allowance, then read the coverage.

Here is what each result line means:

A concrete coverage calculator answers the question in reverse. Instead of sizing a slab and asking how much concrete to order, it starts with the concrete, a truckload, a leftover yard or a pallet of bags, and tells you how much area it will cover or how thick it will pour.

That is useful when the amount is fixed: a minimum truck load, the bags already in the garage, or a part load left over from a bigger pour. To go the other way and size an order from a slab, use the concrete slab calculator in the related tools. To check the weight of what you are placing, use the concrete weight calculator, and for a pallet count, the concrete pallet calculator.

Volume is area times thickness, so if you know the volume and the thickness you can divide to get the area. The tool first turns your amount into cubic feet and takes off the waste allowance, because concrete lost to the base and the forms never becomes slab.

1. Convert the amount to cubic feet: cubic yards times 27, or bags times the bag yield.
2. Divide by one plus the waste percentage for the usable volume.
3. For area, divide the usable cubic feet by the thickness in feet; for thickness, divide by the area and multiply by 12.
4. Report the coverage per cubic yard, which at any thickness is 324 divided by the thickness in inches.

For the binder in a hand mix, the cement calculator sizes the cement.

Suppose a ready-mix supplier has a 3 cubic yard minimum and you want to know how big a 4 inch slab it will make, allowing 5 percent waste.

Calculation: 3 cubic yards is 3 x 27 = 81 cu ft. Taking off 5 percent waste leaves 81 / 1.05 = 77.1 cu ft. At 4 / 12 = 0.333 feet thick that covers 231.4 sq ft, about a 15.2 foot square. With no waste allowance it would be 243 sq ft.

The lesson: one cubic yard covers 81 square feet at 4 inches, so a 3 yard minimum is enough for a generous patio, not a driveway.

One cubic yard is 27 cubic feet, so the area it covers is 324 divided by the thickness in inches, before waste.

These are exact geometric figures before any waste. Real coverage is a little lower because of an uneven base and spillage, which is what the waste allowance accounts for.

Thickness

Coverage is inversely proportional to thickness: double the thickness and the same concrete covers half the area. It is the biggest lever on how far a load goes.

Sub-base Flatness

A low or rutted base soaks up concrete below the design line, so real coverage falls short of the geometry. A well-graded, compacted base gets you closer to the figure.

Waste and Spillage

Concrete left in the truck chute, the barrow and the forms never reaches the slab. The waste allowance takes it off before the coverage is worked out.

Bag Yield

Bags are sold by weight but cover by volume. An 80 pound bag yields about 0.60 cubic feet, so a pile of bags covers far less than it looks.

The same coverage takes very different amounts of handling depending on how you buy the concrete.

For the delivered price of a load, the concrete cost calculator in the related tools prices it by the yard.

Using a Minimum Load

When a supplier has a minimum order, find out how much slab it makes so you can plan a second job to use it.

Using Leftover Bags

Check whether the bags you already have will cover a small pad or path before buying more.

Checking a Quote

Enter the yards on a quote and your area to see the thickness it implies, a quick check that the order matches the slab.

1. Forgetting Thickness Is in Inches

Coverage depends on thickness in feet. The tool converts inches for you; entering feet in the inches field would make coverage look twelve times smaller.

2. Counting Bags by Weight

An 80 pound bag is only about 0.60 cubic feet. Assuming bags cover more than their yield leaves you short.

3. Ignoring Waste

The geometric figure assumes every bit of concrete ends up in the slab. Keep a waste allowance so the coverage reflects what you can actually place.

4. Thinning the Slab to Stretch a Load

Pouring thinner than the job needs to make a load reach further risks cracking. Fit the area to the concrete, not the thickness.

5. Treating Coverage as a Thickness Spec

This tool tells you how far concrete goes; it does not tell you how thick a slab should be. That comes from your plans or code.

The arithmetic is exact; real coverage depends on the base and the waste you allow.

At 4 inches thick, one cubic yard covers 81 square feet before waste. In general it covers 324 divided by the thickness in inches, so 108 square feet at 3 inches and 54 square feet at 6 inches. Allow 5 to 10 percent less for waste.

At 4 inches thick, 3 cubic yards covers 243 square feet with no waste, or about 231 square feet with a 5 percent allowance. That is roughly a 15 foot square slab. Enter your own thickness above.

An 80 pound bag yields about 0.60 cubic feet, so at 4 inches thick it covers about 1.8 square feet, and at 2 inches about 3.6. It takes about 45 bags to make one cubic yard.

Divide the usable volume in cubic feet by the area in square feet and multiply by 12 for inches. Two cubic yards over 200 square feet, with 5 percent waste, pours about 3.09 inches thick, which is thin for most slabs.

Because concrete lost to the base, the forms and the truck never becomes slab. Taking the waste off the amount gives the coverage you can actually expect, not the theoretical maximum.

Yes. Switch to thickness mode, enter the yards on the quote and your slab area, and it shows the thickness the order implies. If it is well under the thickness you need, the order is short.

It is the reverse. The slab calculator starts from a slab and tells you how much concrete to order; this one starts from an amount of concrete and tells you how much slab it makes.

No. The calculation runs entirely in your browser and nothing you enter is stored or sent anywhere.

• QUIKRETE Concrete Mix 1101 data sheet (QUIKRETE; bag yields 0.60, 0.45 and 0.30 cu ft).
• National Ready Mixed Concrete Association (NRMCA; ready-mixed concrete and ordering).
• American Cement Association (American Cement Association; concrete basics).