How to Calculate Yards of Concrete: A Simple Guide for Your Next Project

Publish on: 28-Mar-2025

Planning a concrete project like a patio, driveway, or slab? One of the most important steps before you pour is knowing exactly how much concrete you need. Ordering too little can delay your project, while too much can be a waste of money. That’s where calculating yards of concrete comes in.

In this beginner-friendly guide, we’ll walk you through how to calculate the cubic yards of concrete required for any project. No fancy math degree needed—just some simple measurements, a basic formula, and a calculator.

What Is a Cubic Yard of Concrete?

First things first—a cubic yard is a unit of volume. One cubic yard equals 27 cubic feet (3 feet long × 3 feet wide × 3 feet deep). In concrete terms, this is the standard unit used when ordering from a supplier or mixing large batches.

So, when someone says “you’ll need 2 yards of concrete,” they mean 2 cubic yards, which equals 54 cubic feet of concrete.

The Basic Formula: Length × Width × Depth

To find how much concrete you need, follow this simple formula:

Length (ft) × Width (ft) × Depth (ft) ÷ 27 = Cubic Yards of Concrete

Let’s break it down:

Measure the area you’re going to fill with concrete in feet.
Multiply the length × width × depth to get the volume in cubic feet.
Divide by 27 to convert cubic feet to cubic yards.

Step-by-Step Example: Concrete Slab

Let’s say you’re pouring a concrete slab for a small patio.

Length: 10 feet
Width: 10 feet
Depth (thickness): 4 inches (which is 0.33 feet)

Now plug these into the formula:

10 × 10 × 0.33 = 33 cubic feet
33 ÷ 27 = 1.22 cubic yards

So, you’d need about 1.25 cubic yards of concrete (always round up slightly to account for spillage or errors).

How to Convert Inches to Feet

Since concrete thickness is usually measured in inches (like 4", 6", or 8"), you’ll need to convert inches to feet before plugging into the formula.

Here’s a quick cheat sheet:

Inches	Feet
4"	0.33 ft
6"	0.5 ft
8"	0.66 ft
12"	1 ft

So if your slab is 6 inches thick, you’ll use 0.5 ft as the depth in the formula.

Common Project Sizes and Concrete Needs

Here are a few rough estimates to help visualize typical concrete requirements:

Project Type	Size (ft)	Thickness	Approx. Concrete Needed
Sidewalk Section	4 × 10	4"	0.5 cubic yards
Driveway (1 car)	10 × 20	6"	3.7 cubic yards
Patio	12 × 12	4"	1.8 cubic yards
Shed Foundation	10 × 10	6"	2.2 cubic yards

These are estimates. Always measure your project area carefully.

Use a Concrete Calculator

Want to skip the math? Use an online Concrete Slab Cost Calculator (insert your tool link here) to plug in your dimensions and get an instant estimate. These tools save time and help you avoid over- or under-ordering.

Always Order a Little Extra

Here’s a pro tip: always add 10% extra to your concrete order. This covers any spillage, uneven ground, or last-minute changes in your plan.

So if your total need is 2.5 cubic yards, order 2.75 or even 3 cubic yards to be safe.

Conclusion

Calculating how many yards of concrete you need isn’t rocket science—it just takes a few measurements, a little math, and some smart planning. Whether you’re pouring a slab, walkway, or driveway, using the simple formula of Length × Width × Depth ÷ 27 will ensure your project goes smoothly.

And when in doubt? Use a calculator or consult with your concrete supplier. It’s always better to be a little over than to come up short mid-pour.