Our concrete calculator can determine the amount of concrete you need for a slab, square footing, wall, cylinder, steps, or curb and gutter system. Enter your measurements in feet, inches, yards, meters, or centimeters, and our calculator will display the corresponding volume and weight. It will even tell you how many 60 lb. or 80 lb. bags of concrete to purchase for your project.
Those who prefer double-checking with manual calculations can find concrete usage formulas below.
How Concrete is Sold
Concrete comes in cubic yards and cubic feet. You can order premixed concrete by the yard, while bags of Quikrete and similar brands are sold by the cubic foot.
Bags of concrete come in four sizes – 40, 50, 60, and 80 lb bags.
- A 40 lb bag of concrete covers 0.011 yards or 0.3 cu ft.
- One 50 lb bag of concrete covers 0.013 cubic yards or 0.37 cu ft.
- A 60 lb bag of concrete covers 0.017 cu yards or 0.45 cu ft.
- An 80 lb bag of concrete covers 0.022 cu yards or 0.60 cu ft.
Depending on the bag size, there are between 40-80 bags of concrete on one pallet. There are 80 bags of 40 lb concrete on a pallet, 64 bags of 50 lb concrete, 56 bags of 60 lb concrete, and 42 bags of 80 lb concrete.
How to Estimate Concrete for Slabs, Square Footings, or Walls
Figuring concrete needs for simple square or rectangular slabs is simple. To determine cubic feet of concrete, multiply your project’s length, width, and depth/height in feet.
Cubic feet = length (ft) x width (ft) x height/depth (ft)
If ordering concrete by the cubic yard, divide your cubic feet measurement by 27.
Cubic yards = length (ft) x width (ft) x height/depth (ft) ÷ 27
Here’s an example: We’re pouring a small slab 12′ long, 10 feet wide, and 6 inches or 0.5′ deep.
- Cubic feet = 12 x 10 x 0.5
- 60 Cubic feet = 12 x 10 x 0.5
- Cubic Yards = 12 x 10 x 0.5 ÷ 27
- 2.22 Cubic Yards = 12 x 10 x 0.5 ÷ 27
How to Calculate Concrete for Holes, Columns, or Round Footings
If you need concrete for a column or circular footing, the formula for cubic yards and cubic feet differs.
Cubic yards = radius in ft x radius in ft x depth in ft x pi ÷ 27
Cubic feet = radius in ft x radius in ft x depth in ft x pi
Here’s an example: We’ll pour a circular patio with a 10-foot diameter or 5-foot radius. We want our patio concrete to be 4 inches thick, equivalent to 0.3 feet. We’ll use 3.14 for pi.
- Cubic feet = 5 x 5 x 0.3 x pi
- 23.55 Cubic Feet = 5 x 5 x 0.3 x pi
- Cubic Yards = 5 x 5 x 0.3 x pi ÷ 27
- 0.87 Cubic Yards = 5 x 5 x 0.3 x pi ÷ 27
Note: If you’re using our calculator and not making manual calculations, you’ll only need the circle’s diameter, not the radius. The diameter is the length from one side of the circle to the other. The radius is half of the diameter.
How to Estimate Concrete for Annular Cylinders or Rings (Cylinders with Holes in the Middle)
When estimating concrete for a circular tube, you must know the diameter of the outside of the circle, the inside of the circle, and the desired concrete depth. You’ll need to subtract the inner diameter volume from the outer diameter volume for an accurate calculation.
The easiest way to calculate concrete tubes with an open hole is to use our calculator above. You can also use the following equation:
Volume of the outer cylinder – volume of the hole = concrete needed
- First, determine the volume of the outer circle by using this equation: Cubic yards = radius in ft x radius in ft x depth in ft x pi ÷ 27
- Next, determine the volume of the inner circle using this equation: Cubic yards = radius in ft x radius in ft x depth in ft x pi ÷ 27
- Subtract the inner circle’s volume from the outer circle’s volume.
Example: You want to fill the outer edge of a round patio with concrete, you’ll use pea gravel to fill in the middle. The outer edge has a radius of 6 feet and a depth of 4 inches, or .3 feet. The inner circle has a radius of four feet and a depth of 4 inches.
- Cubic Yards of Outer Circle: 6’ x 6’ x .3’ x pi ÷ 27
- Cubic Yards of Outer Circle = 1.256
- Cubic Yards of Inner Circle = 4’ x 4’ x .3’ x pi ÷ 27
- Cubic Yards of Inner Circle = 0.558
- 1.256 – 0.558 = 0.698 Cubic Yards of Concrete Needed
How to Estimate Concrete for Stairs
Calculating concrete for stairs requires several steps. The easiest way to determine accurate estimates is to enter the tread depth, riser height, width, platform depth, and number of steps into our calculator. You can pick your preferred measurements, and the calculator will formulate the weight and volume of concrete for your project.
To manually calculate the amount of concrete you need to pour stairs, break down the stairs into rectangles, find the volume of each, and then add them together.
For example, pretend you are looking at your stairs from the side. Each step, starting from the tallest, is one rectangle. Measure each rectangle’s height, depth, and width in feet and multiply those numbers by each other. Once you’ve determined the volume for each section, add the numbers together. The result is the cubic feet of concrete needed. To determine cubic yards, divide the total cubic feet by 27.
How to Estimate Concrete for Curbs and Gutter Barriers
A curb is a short wall that runs between a street and a yard. Attached to it is a gutter, which is a flat slab of concrete that directs water away from yards. Calculate the volume for each section and add them together to determine total concrete needs.
Curb Volume in Cubic Yards = length (ft) X width (ft) x height (ft) ÷ 27
Gutter Volume in Cubic Yards = length (ft) X width (ft) x height (ft) ÷ 27
Total Cubic Feet of Concrete = Curb Volume + Gutter Volume
