Concrete Coverage Calculator: How Many Square Feet Does a Yard of Concrete Cover?
If you're planning a concrete project like a driveway, patio, or foundation slab, one of the most important calculations is determining how much concrete you'll need. The coverage area of a cubic yard of concrete depends on the thickness of the pour. Learn exactly how many square feet a yard of concrete covers at various slab depths to estimate your concrete needs for any project.
What is a Cubic Yard of Concrete?
Before looking at coverage, it's helpful to understand precisely what a cubic yard is when it comes to concrete. A cubic yard is simply a unit of volume measurement. Specifically, it is the volume of a cube with each side measuring 1 yard or 3 feet.
So a cubic yard of concrete is the amount of concrete it would take to fill a cube shaped container with 3 foot long sides. This works out to 27 cubic feet of volume (3 x 3 x 3).
On average, one cubic yard of mixed concrete contains:
- 4000 lbs of concrete (around 2 tons)
- 35-40 sixty-pound bags of premix concrete
- 1.4 cubic meters in the metric system
Knowing the weight and volume measurements for a yard of concrete makes it easy to estimate how many bags or truckloads you might need for a project. But to find out the specific coverage area, you need to consider the thickness of the pour.
Concrete Thickness Impact on Coverage
One of the key factors in determining square footage covered per cubic yard is slab depth. As the thickness of the concrete increases, the coverage area for a given volume decreases. This is because it requires more concrete to cover the same footprint at a greater depth.
As you can see, for a typical 4" slab, you'll need around 1 yard of concrete per 80 square feet of area. But at 12" thickness, that coverage is reduced to only 27 square feet per yard. So calculating depth is crucial for accurately estimating how much concrete is required.
Coverage Per Inch of Concrete
An easy way to calculate the coverage for any thickness is to break it down inch by inch.
As the depth increases, the coverage area decreases because it takes more concrete to fill the extra inch of thickness across a given footprint. This per inch estimate makes it easy to quickly calculate coverage for any pour depth you need.
Factors That Influence Concrete Coverage
While depth is the primary factor, there are some other elements that can impact the coverage area of a cubic yard of concrete:
- Concrete strength - Higher strength concrete is denser and heavier, resulting in slightly less coverage per yard.
- Reinforcing steel - The addition of rebar or mesh for reinforcement takes up volume, decreasing coverage.
- Shape of area - Simple squares or rectangles maximize coverage vs. complex curves and angles.
- Dimensions - Smaller total size increases coverage as less is lost to mixers and tools.
However, in most cases these have a relatively minor effect. Focusing on the depth and using the reference charts above will give you a highly accurate yardage estimate.
Estimating Concrete for DIY Projects
For homeowners and DIYers taking on smaller concrete projects, accurately estimating how much concrete you'll need is crucial. Here are some tips for success:
- Carefully measure the length and width of the area you need to pour in feet, then multiply to get the total square footage.
- Decide on the thickness in inches - 4 to 6 inches is typical for patios and driveways.
- Use the coverage info above to determine how many square feet each yard of concrete will cover at that thickness.
- Divide your total area by the per yard coverage to estimate the cubic yards required.
Let's look at a quick example:
Say you're pouring a 100 square foot patio at 4 inches thick. You know from the chart that at 4", one yard covers 81 sq ft. Dividing 100 sq ft by 81 sq ft per yard gives you an estimate of 1.2 cubic yards.
To give yourself a safety buffer, you would round up and order 2 yards total for this 100 square foot patio. Having an extra partial yard on hand prevents you from running short.
Concrete Coverage Calculator
For quick concrete estimates, use this handy calculator. Simply input your slab thickness and total area in square feet:
Inputs
- Thickness: ___ inches
- Area: ___ square feet
Output
- Cubic yards required:
With just the depth and square footage, you can instantly calculate the approximate cubic yards required. No more guessing or complex formulas needed!
Concrete Coverage Cheat Sheet
Use this handy reference chart for a quick overview of cubic yards of concrete needed per square foot of coverage area:
| Slab Thickness | Square Feet Covered |
|---|---|
| 4 inches | 81 sq ft |
| 5 inches | 65 sq ft |
| 6 inches | 54 sq ft |
| 8 inches | 40 sq ft |
| 12 inches | 27 sq ft |
With this handy reference, you can quickly look up coverage amounts for standard thicknesses. No calculations needed!
Frequently Asked Questions
How do I calculate how many cubic yards of concrete I need?
Measure the area's square footage, choose the thickness in inches, then divide the total area by the coverage per yard at that depth. This gives an estimate of the yards needed. Add 10-20% as a safety factor.
Does the strength of concrete impact coverage?
Yes, higher strength concrete weighs more so yields slightly less coverage per yard, but strength has a minor effect compared to depth.
How do I allow for irregular shapes when estimating?
Divide the area into simple squares and rectangles, calculate each separately, then add together for total yards. This accounts for complex layouts.
Why does coverage decrease with thickness?
A greater depth requires more concrete to fill, so a yard spreads over less area. At double the depth, the coverage is roughly halved.
Should I include an extra margin when ordering concrete?
Yes, it's wise to order 10-20% more than estimated to account for spillage, uneven slabs, and other factors. Avoid running short halfway through pouring.
You can easily estimate your concrete requirements with the right information. Remember that coverage decreases as depth increases. Use the handy charts and calculator to determine the yards needed based on your project's footprint and thickness. And be sure to add extra margin when ordering. With these tips, you'll know exactly how many square feet a yard of concrete covers and have plenty to complete your next project.