How Many Yards of Concrete Do I Need?
Enter the size of your pour and get the cubic yards of concrete to order, with the waste allowance added and the working shown. A slab that is not a rectangle can be drawn with Draw a shape.
A ready-made setup of the Concrete Calculator.
Estimates for planning, not professional advice. Read the full notice.
The drawing did not open. Length and width are still here.
Slab: shape and size
Skip the drawingDrag a round corner to move it. The small hollow diamond on a side is its curve handle: drag it across the side to curve the side (it is not a corner). To add a corner (a new point), tap the side itself, then choose Add a point here. Tapping a corner or a side opens its actions. Drag empty space to move the view; pinch, or Ctrl and the mouse wheel, to zoom. The keys are listed under Keys.
Keys
- Tab
- next corner; each says how far it is from corner 1
- Arrow keys on a corner
- move it one square; ten with Shift; 1/16 in with Alt
- Delete or Backspace
- remove the corner; its two sides join in one straight side
- + on a corner
- add a corner halfway along the next side
- Arrow keys on the drawing
- move the view; farther with Shift
- + and - on the drawing
- zoom in and out
- 0 on the drawing
- show the whole shape
- Ctrl+Z (Cmd+Z on a Mac)
- undo, except inside a typed field (it keeps its own)
- Ctrl+Shift+Z or Ctrl+Y
- redo
- Escape while dragging
- put it back where it was
- Enter on a corner or side
- go to its actions
- Escape in the actions
- close them and go back to the drawing
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- Area
- 576 ft²
- Perimeter
- 96 ft
- Cut-out edges
No area until the shape is fixed.
Estimate for planning, from what you entered and the product data shown. Check product labels and your supplier before you buy.
Shape: Rectangle Change
Sides
Corners
Cut-outs
Feet and inches, like 12' 6"
Example: a driveway pad
12 yd³ to order (11.73 yd³ exact)
- Concrete in the slab 10.67 yd³
Your project
Enter a size to see your total.
Each product is rounded up once for the whole project, so the total can be less than the items bought alone added together. A line counted from a cut layout (sheets, boards or tiles laid out piece by piece) is counted for each item and added.
Shopping list
| Item | Size | Buy |
|---|---|---|
| Ready-mix concrete | 1 yd³ | 12 yd³ |
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Saved projects
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Worked example: a driveway pad
Show the working
- Slab area 24 ft × 24 ft = 576 ft²
- Slab volume 576 ft² × 6 in = 10.67 yd³
- Add the waste allowance 10.666667 yd³ + 10%[1] = 11.73 yd³
Assumptions
The figures behind the example. Sourced figures link to their source below; a default is a starting value to check against your label or supplier.
| Assumption | Value | Details and changes |
|---|---|---|
| Concrete waste allowance | 10%[1] | |
| Default 10% is the top of NRMCA's 4% to 10% range. | ||
Feet and inches, like 12' 6"
Common jobs
Concrete to order for common jobs
| Job (length × width × thickness) | Concrete, with waste (exact) | Concrete to order |
|---|---|---|
| 24 ft × 24 ft × 6 in | 11.73 yd³ | 12 yd³ |
| 40 ft × 16 in × 8 in | 1.45 yd³ | 1.5 yd³ |
| 20 ft × 4 ft × 8 in | 2.17 yd³ | 2.5 yd³ |
Both columns include the waste allowance. The order is the exact figure rounded up once, to the supplier's ordering step.
Questions
How many yards of concrete do I need?
Multiply the length, width and thickness to get the volume, add a waste allowance, and read the total in cubic yards. The calculator shows the exact volume and the yards to order at your supplier's step, with every step.
Why is the amount to order more than the exact volume?
Ready-mixed concrete is ordered in steps set by the supplier. The calculator adds the waste allowance to the exact volume and rounds up once, to the supplier's step, and it shows both figures.
Why round up only once?
Rounding each part of a job first can add or drop a step of the order. The calculator adds the exact volumes, puts the waste allowance on the total, and rounds up once, to the supplier's step, at the end.
How much does a yard of concrete cost?
Your supplier sets the price, and it changes with the mix, the delivery and any small-order charge, so this page does not give one. Ask for the price per yard and multiply it by the yards to order.
Sources (1)
-
CIP 31, Ordering Ready Mixed Concrete (opens in new tab), National Ready Mixed Concrete Association, 2000, 2016, 2023.
Standards or industry body.
“Quantity of concrete ordered should be 4% to 10% more than an estimate calculated from the plan dimensions to account for contingencies.”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 1)
These are summaries of what the sources say, not professional advice. Codes and product data change. Check with your building department and the product label about your own project.
Sources
- [1] National Ready Mixed Concrete Association, CIP 31, Ordering Ready Mixed Concrete. Checked November 12, 2026. https://www.nrmca.org/wp-content/uploads/2021/01/31pr.pdf