Concrete Calculator
Calculate the exact volume of concrete needed for your project in cubic meters, plus estimated cement bags required.
Concrete Calculator
Calculate concrete volume in cubic meters.
Concrete Volume
0.00 m³A concrete calculator saves you from the two most common and costly ordering mistakes: running out mid-pour, or paying for far more ready-mix than you actually needed. Enter the length, width, and depth of your slab, footing, or column, and Toolnix instantly returns the exact volume required, converted into cubic yards, cubic feet, or cubic meters, along with the equivalent number of standard concrete bags if you plan to mix by hand instead of ordering a truck.
What This Concrete Calculator Covers
This tool handles the most common residential and small commercial concrete projects, including slabs, footings, columns, and sidewalks. It converts your project dimensions into total volume, then translates that volume into practical purchasing units.
For DIY projects using bagged concrete mix, it shows the number of 40 pound, 60 pound, and 80 pound bags needed. For larger pours where ready-mix delivery makes more sense, it shows the total cubic yards to order, which is the standard unit concrete suppliers use for quoting and delivery.
How to Calculate Concrete Volume Correctly
Start by measuring the length and width of the area you are pouring, in feet or meters depending on your preferred unit. Then measure the depth, or thickness, of the slab or footing, which is often given in inches for slabs.
Measure Length & Width
Use feet or meters, whichever matches how your project is drawn or staked out.
Measure the Depth
Slab thickness is usually quoted in inches — enter it exactly as measured.
Calculate and Order
Read your volume in cubic yards, cubic feet, or meters, plus the bag count.
Enter these three measurements into the calculator, and it multiplies them together to find total volume. For slabs measured in feet and inches, the tool automatically converts inches to a decimal foot value before multiplying, then divides the cubic foot result by 27 to give you cubic yards, which is how most ready-mix suppliers price and deliver concrete.
The Concrete Volume Formula Behind the Tool
The underlying math is simple: volume equals length multiplied by width multiplied by depth. The complexity usually comes from unit conversion rather than the formula itself.
Cubic Yards = Length (ft) × Width (ft) × Depth (ft) ÷ 27
Depth in inches ÷ 12 gives depth in feet • 27 cubic feet = 1 cubic yard
A standard driveway slab, for example, might be 20 feet long, 10 feet wide, and 4 inches thick. Converting 4 inches to 0.333 feet and multiplying gives about 66.7 cubic feet, which equals roughly 2.5 cubic yards once divided by 27. This calculator runs every step of that conversion automatically, removing the risk of a decimal error that could leave you short on pour day.
Quick Reference: Common Slab Sizes
| Slab Size | Thickness | Cubic Feet | Cubic Yards | Order With 10% Buffer |
|---|---|---|---|---|
| 10 × 10 ft | 4 in | 33.3 | 1.23 | 1.36 |
| 12 × 12 ft | 4 in | 48.0 | 1.78 | 1.96 |
| 20 × 10 ft | 4 in | 66.7 | 2.47 | 2.72 |
| 20 × 20 ft | 4 in | 133.3 | 4.94 | 5.43 |
| 24 × 24 ft | 6 in | 288.0 | 10.67 | 11.73 |
Ordering Tips That Prevent Common Mistakes
Experienced contractors almost always add a buffer to their calculated volume, and this calculator recommends the same approach. Adding 5 to 10 percent extra covers spillage during the pour, minor variations in subgrade depth, and any small measurement error.
It is also worth rounding up to the nearest full bag when mixing by hand, or checking your local supplier's minimum order quantity when ordering ready-mix, since many suppliers charge a short-load fee for orders below a certain volume threshold.
Running short mid-pour is far more expensive than over-ordering. A cold joint where fresh concrete meets partially set concrete creates a permanent weak line in the slab.
Choosing Between Bagged Mix and Ready-Mix Delivery
For small pours, typically under half a cubic yard, bagged concrete mix from a hardware store is usually more practical and often cheaper once delivery fees are factored in. For anything larger, a ready-mix truck delivers a consistent, professionally batched mix in a fraction of the time it would take to hand-mix dozens of bags.
Bag Yield per Cubic Yard
| Bag Size | Approx. Yield | Bags per Cubic Yard |
|---|---|---|
| 40 lb | 0.30 cu ft | 90 bags |
| 60 lb | 0.45 cu ft | 60 bags |
| 80 lb | 0.60 cu ft | 45 bags |
This calculator shows both figures side by side, so you can compare the bag count against the equivalent cubic yardage and decide which approach fits your project size and budget.
Frequently Asked Questions
Roughly 45 bags of 80 pound concrete mix make up one cubic yard, or about 60 bags of 60 pound mix, though this varies slightly depending on the specific mix and bag weight you choose.
Multiply the slab's length by its width by its depth to get cubic feet, then divide that figure by 27 to convert it into cubic yards, which is the standard ordering unit.
Yes, adding 5 to 10 percent extra is standard practice among contractors and covers spillage, uneven subgrade, and small measurement inaccuracies that are common on real job sites.
Most residential driveways use a slab thickness between 4 and 6 inches, with 6 inches recommended if the driveway will regularly support heavier vehicles.
Yes, enter the footing or column dimensions the same way you would a slab, using length, width, and depth, and the calculator applies the identical volume formula.
For small projects under about half a cubic yard, bagged mix is usually more cost-effective, while ready-mix delivery becomes more economical for larger pours despite delivery fees.