Concrete FAQ

Measure the length, width and thickness of the space you want to fill, multiply them together to get a volume, then divide by 27 to convert cubic feet to cubic yards. Our calculator does this for you: enter the dimensions of each shape and it adds everything up, including extra for wastage.

A cubic yard is 27 cubic feet (3 ft x 3 ft x 3 ft). At a typical 4-inch slab thickness, one yard covers about 81 square feet. At 5 inches it covers about 64.8 square feet, and at 6 inches about 54 square feet.

It depends on the bag size. Using typical yields, one 80 lb bag produces about 0.60 cubic feet, so a cubic yard takes roughly 45 of them. A 60 lb bag yields about 0.45 cubic feet (about 60 bags per yard) and a 40 lb bag about 0.30 cubic feet (about 90 bags per yard). Always round up and check the yield printed on the bag you buy.

Small jobs such as a few post holes or a landing are usually easier with bags. Anything around a cubic yard or more is often simpler as a ready-mix delivery. Our cost calculator compares both options for your own prices and shows the volume where one becomes cheaper than the other.

Real pours lose material to spillage, uneven ground, over-excavation and what stays in the mixer or wheelbarrow. A common allowance is 10%, which you can adjust between 0% and 20% on the calculator. Skipping this allowance is one of the most common reasons a pour runs short.

Walkway and patio slabs are often around 4 inches thick, while driveways are usually thicker. The right thickness depends on what the slab carries, the soil and local practice. Our calculator does not set thickness requirements: enter whatever thickness your project plans call for.

You cannot buy a fraction of a bag, so bag counts are always rounded up to the next whole bag. That rounding, plus the wastage allowance, is why the bag count is often a little above the raw volume.

It gives you a sense of the scale of the job and helps you plan how many loads your vehicle or cart can handle. The estimate uses a typical density of 150 lb per cubic foot, which you can change if you have a different value.

On the home calculator you can add up to ten pours, each with its own shape, dimensions and quantity. The tool lists each pour's subtotal and adds everything into one grand total. The project lives only in your browser: nothing is uploaded, and clearing or closing the page erases it.

It sketches the shape you selected with your dimensions drawn on it. The drawing updates roughly as you type so you can spot a mistyped number, but it is an illustration, not a scale drawing of your site.

Slabs are usually poured over a compacted gravel base rather than raw soil. The slab calculator estimates the volume and weight of that base from the slab area and the depth you enter, so you can plan that material separately.

Yes. Every calculator has an imperial/metric switch. Internally the math is the same; your inputs are simply converted, and results are shown in cubic meters and kilograms as well as cubic yards and pounds.

Use the Copy summary button to place a plain-text summary on your clipboard, or Print for a one-page sheet you can save as a PDF. Neither stores anything anywhere else.

Prices vary a lot by region, supplier and order size, and they change over time. That is why our calculators show no default prices: you enter your own quotes from local suppliers, and the tools compare them. Any figures used in the worked examples are illustrations only.

Suppliers charge for the truck trip, so they commonly sell in minimum loads, often several yards. If your job is smaller than the minimum, you pay for the full minimum anyway. Our cost calculator has a field for that minimum so the comparison stays honest for small jobs.

Ready-mix begins to set after it is batched, so delivery windows matter and are arranged with the supplier at ordering time. Ask them about their scheduling when you request a quote.

No. Everything on this site is an estimate for planning, based on the values you enter and typical material yields. Quantities and costs depend on site conditions and your suppliers. Confirm with your own suppliers and local building authorities before you buy.