Concrete Calculator: Cubic Yards, Bags and Cost
A concrete calculator finds how much concrete you need in cubic yards, cubic meters and bags, then turns that volume into a ready-mix order or bag count and an estimated cost. Enter the length, width and thickness of a slab, or the diameter and depth of a footing or column, and it handles the length times width times thickness math and the divide by 27 conversion for you. Below is exactly how that formula works, what concrete costs per cubic yard in 2026, and when to buy bags instead of ordering a truck.
Key takeaways
- Cubic yards equal length x width x thickness (all in feet) divided by 27; add 5 to 10% for waste.
- A 10x10 ft slab at 4 inches needs about 1.23 cubic yards, or 1.36 with waste, roughly 62 bags of 80 lb mix.
- Ready-mix concrete runs about 125 to 185 dollars per cubic yard delivered in 2026, averaging near 145 to 165 dollars.
- One cubic yard equals 27 cubic feet and weighs about 4,050 pounds, roughly 45 bags of 80 lb mix.
- Bags cost more per yard than ready-mix; jobs over about 1 to 1.5 cubic yards are usually cheaper by the truck.
The concrete calculator formula: cubic yards, cubic feet and bags
A concrete calculator turns three measurements, length, width and thickness, into a volume, then converts that volume into cubic yards, bags and a cost. For any rectangular pour, multiply length by width by thickness in feet, dividing the thickness in inches by 12 first.
One cubic yard equals 27 cubic feet, so the last step is dividing the cubic-foot volume by 27. Concrete weighs about 150 pounds per cubic foot, near 4,050 pounds per cubic yard, which the calculator uses to estimate delivery weight.
Volume (ft3) = Length(ft) x Width(ft) x (Thickness(in) ÷ 12)Cubic yards = Volume(ft3) ÷ 27Always add 5 to 10% for waste, since subgrade is never perfectly flat and a truck cannot come back mid-pour. The concrete calculator runs this math for slabs, footings, round columns, tubes, curbs and stairs, and adds the waste factor automatically.
How much does concrete cost per cubic yard in 2026
Ready-mix concrete costs about 125 to 185 dollars per cubic yard delivered in 2026 for a standard 3,000 to 4,000 PSI mix, with the national average clustering near 145 to 165 dollars. Higher-strength mixes add roughly 8 to 30 dollars per yard depending on PSI.
| Mix / order size | Typical cost |
|---|---|
| 3,000 PSI ready-mix, per yard | $125 to $165 |
| 4,000 PSI ready-mix, per yard | $140 to $185 |
| Short-load fee (under truck minimum) | $40 to $150 |
| 80 lb bag, bagged concrete | about $6 |
Bagged concrete costs more per yard, about 270 to 290 dollars once you buy the roughly 45 bags of 80 lb mix a cubic yard takes. Orders under about a yard are usually still cheaper in bags once delivery minimums are counted.
Delivery distance, weekend pours and fuel surcharges add more on top. Expect 9 to 15 dollars per mile beyond a 20 mile radius, and 50 to 100 dollars for a Saturday delivery.
Concrete calculator for slabs, patios and driveways
For a slab, patio or driveway, the calculator needs only length, width and thickness. A 10 by 10 foot patio at 4 inches thick comes out to about 1.23 cubic yards, or 1.36 with a 10% waste allowance.
Driveways carry more weight, so they are typically poured 5 to 6 inches thick rather than the 4 inches used for a patio or walkway, which raises the volume by a quarter to a half for the same footprint.
The concrete slab calculator is built specifically for this shape: enter the dimensions and thickness and it returns cubic yards, bag counts and an optional cost in one step.
Concrete calculator for footings, posts and round columns
Footings, fence posts and round columns use a different shape and need their depth and width in inches rather than feet. A 40 foot strip footing 16 inches wide and 8 inches deep works out to about 1.45 cubic yards including waste.
Round piers and post holes use a cylinder formula, pi times radius squared times height, since forcing a circle into a rectangle formula overstates the concrete needed.
The footing calculator handles strip footings, round piers and post holes without any manual conversion, and flags whether bags or a ready-mix order fits that volume.
How many bags of concrete are in a cubic yard
One cubic yard, 27 cubic feet, takes about 45 bags of 80 lb concrete mix, 60 bags of 60 lb, or 90 bags of 40 lb, since each bag yields roughly 0.60, 0.45 and 0.30 cubic feet.
Mixing 45 bags by hand is a full day of labor for two people, which is why jobs over about 1 to 1.5 cubic yards are usually better ordered as ready-mix instead. The full breakdown, including yields for every bag size, is in how many bags of concrete are in a yard.
Common mistakes that throw off a concrete estimate
The most common estimating mistake is forgetting the waste factor, since a slab poured even a half inch over its nominal thickness adds up fast across a large footprint. Add 5 to 10% and round up rather than down.
The second mistake is mixing units, entering thickness in feet instead of inches or forgetting to convert before multiplying. Keep length and width in feet, thickness in inches divided by 12, and let the calculator carry the rounding.
Frequently asked questions
How do you calculate how much concrete you need?
How much does a cubic yard of concrete cost in 2026?
How many bags of concrete do I need for 1 cubic yard?
How much does a concrete calculator save compared to guessing?
How much concrete does 1 yard cover?
References
- Concrete (Wikipedia)
- NRMCA: Ready Mixed Concrete
- ACI 332: Residential Concrete Code
- QUIKRETE Concrete Mix