Concrete Calculator
Find out how much concrete you need for your next project. This free concrete calculator estimates the volume of concrete required for slabs, patios, driveways, footings, and other rectangular projects. Enter your measurements, choose your units, and get the result in cubic yards, cubic feet, and cubic meters.
Whether you’re preparing a small DIY project or planning a larger concrete pour, this calculator helps you estimate the quantity before ordering.
Concrete Calculator
Calculate the amount of concrete you need for your project.
Enter Your Measurements
Waste Allowance
Concrete volume = Length × Width × Thickness
For cubic yards, divide the volume in cubic feet by 27. The calculator automatically converts your measurements.
How Much Concrete Do I Need?
To calculate the amount of concrete needed for a rectangular slab, multiply its length by its width and thickness.
For example, a concrete patio that is 20 feet long, 12 feet wide, and 4 inches thick requires approximately 2.96 cubic yards of concrete before adding a waste allowance.
With a 10% allowance, the estimated amount to order is approximately 3.25 cubic yards.
The calculator above performs this calculation automatically and lets you adjust the measurements to match your project.
How to Use the Concrete Calculator
- Select your preferred measurement system: feet and inches or meters and centimeters.
- Enter the length of your concrete area.
- Enter the width.
- Enter the thickness or depth of the concrete.
- Choose a waste allowance if you want to account for minor variations, spillage, or uneven ground.
- Click Calculate to see your estimated concrete volume.
The result shows how much concrete your project requires before waste and the adjusted quantity after the allowance.
If you are ordering ready-mix concrete, use the adjusted quantity as a planning estimate and confirm the final order with your supplier.
Concrete Calculator Formula
The basic formula for a rectangular concrete slab is:
Concrete volume = Length × Width × Thickness
All three measurements must use the same unit.
For example, if you measure a slab in feet, convert its thickness from inches to feet before multiplying.
A slab measuring 15 feet long, 10 feet wide, and 4 inches thick has a volume of:
15 × 10 × (4 ÷ 12) = 50 cubic feet
To convert cubic feet to cubic yards:
50 ÷ 27 = 1.85 cubic yards
The estimated concrete volume is therefore 1.85 cubic yards before adding any waste allowance.
Related Concrete Calculators
Need to calculate concrete for a specific project? Try one of these calculators:
- Concrete Slab Calculator: Estimate the concrete needed for a rectangular slab, garage floor, or foundation slab.
- Concrete Patio Calculator: Calculate the amount of concrete needed for a patio based on its dimensions.