Concrete Calculator
Concrete Calculator
Estimate the volume and weight of concrete needed for your construction project. Supports slabs, walls, columns, curbs, and stairs.
Cubic Feet
5.21 ft³
Cubic Meters
0.15 m³
60-lb Bags
12
80-lb Bags
9
* Based on a standard pre-mixed density of 133 lbs/ft³. Actual yield may vary by concrete brand and water mix.
Worked Examples
Estimating materials for a 10' x 10' patio slab at a standard 4-inch thickness. The calculator determines you need exactly 1.23 cubic yards of concrete.
If purchasing pre-mixed bags, you will need approximately 56 bags of 80lb concrete. Adding a 10% safety margin brings the recommended order to 62 bags.
Calculating concrete for 12 fence post holes, each with a 12-inch diameter and 3-foot depth.
The tool calculates a total volume of 1.05 cubic yards (roughly 2.36 cubic feet per hole). This would require about 48 bags of 80lb concrete to complete the entire fence line.
Take the Guesswork Out of Your Build with MyApexCalc
Whether you are pouring a backyard patio, setting posts for a new fence, building a structural retaining wall, or laying down a driveway, accuracy is everything. Ordering too little concrete leads to cold joints and expensive, delayed secondary deliveries. On the other hand, over-ordering wastes money and leaves you with raw, curing material you have to discard. Our free online Concrete Calculator serves as a highly precise Concrete Estimator, converting your project's physical measurements into exact material quantities in seconds.
The Math of Volume: How to Calculate Cement and Concrete Slabs
Because construction supplies are sold in distinct units—typically cubic yards for bulk ready-mix deliveries or bags for smaller home improvement tasks—you must first calculate the three-dimensional volume of your project.
1. The Standard Slab Formula (Rectangular Prisms)
To estimate the volume of a standard rectangular slab using our concrete slab calculator, you must multiply its length (L), width (W), and thickness or depth (D):
Because dimensions on a job site are usually mixed (such as measuring length and width in feet, but slab thickness in inches), you must first convert your thickness to feet before multiplying:
2. Converting to Bags of Concrete
If you plan to calculate cement or pre-mix bags for a DIY job, the calculator converts your total cubic yards into standard bags. Typical pre-mixed bags yield the following volumes:
- 80 lb Bag: Yields approximately 0.60 cubic feet of mixed concrete.
- 60 lb Bag: Yields approximately 0.45 cubic feet of mixed concrete.
The Golden Rule: Factor in Wastage
When finalizing your order using our material dashboard, we highly recommend adding a 10% spillage and wastage margin to your final total.
On-site factors such as uneven ground excavation, structural form bending, or simple spills during transport can easily reduce your active volume. Adding a safe margin ensures you finish your pour without running short.
Why Estimate Your Materials with MyApexCalc?
Multiple Shape Configurations
Easily calculate volume totals for rectangular slabs, round columns, circular footings, or staircases.
Simultaneous Unit Conversions
View your calculations dynamically outputted in cubic yards, cubic feet, 80-pound bags, and 60-pound bags all at once.
Zero Registration Required
Estimate construction materials directly on-site from your mobile browser without sign-wall delays.