How Many Square Feet in a Standard Concrete Yard?

Pouring a new concrete driveway, patio, or foundation is an exciting project for any homeowner. But before you start mixing cement, it's essential to calculate precisely how much concrete you'll need for the job. Determining the square footage in a yard of concrete is the first critical step.

Knowing the exact area your concrete will cover allows you to order the right amount of materials. It also helps you estimate costs and plan the labor. With some simple math using length, width, and thickness measurements, you can find the square feet in a standard concrete yard.

What is a Yard of Concrete?

When discussing concrete, the term "yard" refers to a cubic yard, which is a volume measurement. One cubic yard equals 27 cubic feet. Since concrete is sold by the cubic yard but applied by the square foot, you'll need to convert between these units.

A standard cubic yard of concrete contains:

• Length: 3 feet
• Width: 3 feet
• Height: 3 feet

This equals a total volume of 27 cubic feet (3 x 3 x 3). Contractors commonly estimate that a yard of concrete will cover about 81 square feet at a typical thickness of 4 inches. However, this varies depending on the actual thickness of your planned slab.

Typical Uses

Some common projects using ready-mix concrete measured in cubic yards include:

• Driveways
• Patios
• Foundations and footings
• Slabs
• Sidewalks
• Steps

Factors Affecting Yield

While a cubic yard of concrete equals 27 cubic feet, the actual coverage area in square feet depends on several factors:

• Slab thickness - thicker concrete will cover less area per yard
• Waste - adding 5-10% extra for waste affects total yards needed
• Design - curved and complex designs use more concrete

To determine the square feet in a yard of concrete for your project, you'll need to account for these factors in your calculations.

Why Square Footage Calculations Matter

Figuring out the square footage when working with concrete is essential for several reasons:

• Allows you to calculate how much concrete you need to order
• Helps accurately estimate project costs
• Lets you plan for labor, forms, and finishing
• Prevents shortages or wasteful overages

With the high cost of concrete, over or under ordering can make a major impact on your budget. Measuring the exact length, width, and thickness of your planned slab will ensure you can find the accurate square footage.

Impact on Costs

Since concrete is priced per cubic yard but applied per square foot, accurate area measurements are critical for estimating costs. Multiplying your square footage by the slab thickness gives the cubic yardage needed. With a per yard price, you can then calculate your total concrete costs.

Labor, forming materials, reinforcement, and finishing work may be estimated per square foot or yard as well. So having the right area measurements will help budget for these expenses too.

The Formula for Calculating Square Feet

Finding the square footage in a concrete yard involves a simple two-step formula:

1. Calculate the area in square feet using length x width.
2. Divide the total square feet by 81 for a 4" slab or 54 for 6".

This will provide the cubic yards of concrete required. Let's walk through an example:

Sample Calculation

Say you are pouring a 15 foot by 20 foot driveway 4 inches thick. The math would be:

• Area = Length x Width
  • = 15 feet x 20 feet
  • = 300 square feet
• For 4" thickness, divide by 81
  • 300 square feet / 81
  • = 3.7 cubic yards

So for this driveway, you would need approximately 3.7 cubic yards of concrete to cover 300 square feet at a 4 inch slab thickness. Rounding up, you would order 4 yards.

Factors That Affect Square Footage Yield

While the standard calculation gives you a good ballpark estimate, the actual yield from a yard of concrete may vary based on several factors:

Slab Thickness

Thicker slabs use more concrete per square foot. At 6 inches thick, divide by 54 instead of 81 to account for the extra volume. Refer to the reference chart below for other thicknesses:

Waste Factor

Due to splash, partly filled batches, and finishing needs, add 5-10% for waste and yield loss. For a 10% waste factor on a 300 sq ft driveway:

• 300 sq ft x 1.10 = 330 adjusted square feet
• 330 / 81 = 4.1 yards with overage

Design Factors

Surface contours, curves, and complex shapes like circles use more concrete than flat rectangular slabs. Consider adding extra yards to account for these design factors.

Typical Slab Thicknesses

Knowing typical thicknesses for different concrete projects helps estimate your yards per square foot:

Driveways

The most common driveway thickness is 4 inches. For a 10% overage on a 15 x 20 ft driveway:

• 15 x 20 = 300 sq ft
• 300 sq ft x 1.1 = 330 sq ft (add 10%)
• 330 / 81 = 4.1 yards (at 4 inch thickness)

Foundations

Foundation footings are often 8"-12" thick. For a 16 linear foot wall:

• 16 ft long x 12 inch thickness = 16 cu ft
• 16 / 27 = 0.6 cubic yards

Slabs

Garage and basement slabs range from 4"-6" thick. For a 400 sq ft garage slab:

• 400 sq ft at 5 inch thickness
• 400 / 67.5 = 5.9 cubic yards

Tools to Help Determine Yardage

For convenience, there are tools to help calculate the cubic yards of concrete needed:

• Calculator apps - Many free apps simplify concrete yardage math
• Web calculators - Online tools like Home Depot's concrete calculator
• Graph paper - Grids help sketch shape dimensions to measure
• CAD programs - 3D modeling yields precise volume measures

These tools remove the guesswork and formulas to provide project-specific concrete requirements. Apps can also estimate material costs and labor time.

When to Consult a Concrete Professional

For simple rectangular slabs like a driveway, patio, or shed footing, you can easily calculate the square feet and yardage yourself. But for more complex projects, consider hiring a pro.

Large Jobs

For extensive concrete work, like new home foundations, engraved patios, or curved driveways, a contractor's expertise is valuable. Their experience translates measurements into accurate concrete quantities.

Complex Shapes

Unique slab shapes with radiuses or complex edges require precision calculations. A professional can determine yardage, even for non-rectangular and contoured designs.

Matching Existing Slabs

To seamlessly tie into existing footings or slabs, precise thickness and depth measurements are needed. Rather than demoing to measure, have a contractor evaluate and recommend yardage.

Tips for Square Footage and Yardage Success

With the right approach and preparation, you can minimize guesswork and waste. Here are some tips:

• Use a drawing with exact measurements rather than estimating
• Account for standard overage amounts in your calculations
• Add extra yards for sculpted or curved design elements
• Have tools like a chop saw and wood stakes available to cut forms and validate dimensions
• Use gravel, sand, or dirt to fill low spots instead of extra concrete

Carefully planning and ordering the yards you need helps prevent cost overruns or delays waiting on additional concrete.

Cost Implications of Yardage Estimates

One cubic yard of concrete costs $120 on average. With labor, materials, and equipment, total project costs can multiply quickly. This makes an accurate yardage estimate critical.

For example, just one extra yard of concrete on a 10 yard driveway job can mean an overrun of more than $1500 when you factor in labor, forms, and finishing.

Be sure to get a quote for total cubic yards rather than just concrete costs. Labor per yard or foot also varies by project complexity. Review the complete price estimate before signing a contract.

Key Takeaways

Figuring square feet in a yard of concrete is essential for every contractor and DIYer. Use these key takeaways as a reference:

• One cubic yard = 27 cubic feet of volume
• Yards are used to purchase concrete
• Square feet measure the coverage area
• Divide total square feet by 81 for a 4 inch slab
• Calculate square feet using length x width
• Add extra yards for thicker slabs and waste
• Precise measurements are critical for cost estimates

With some simple math and dimensions, you can find the cubic yards of concrete required for driveways, foundations, and slabs.

Figuring the square footage in a yard of concrete is an essential first step in any concrete project. Accurately calculating the yards you need based on area prevents ordering mistakes and allows you to estimate costs.

While the thickness and design impact yields, the standard formula provides a good starting point. Careful measurement of your slab dimensions, along with added overage, gives the cubic yards required for a successful pour.