Concrete Calculator

Calculate cubic yards or meters of concrete needed for slabs, footings, and columns with optional waste factor.

Loading...
1. Select the shape of your pour - slab, footing, or column. 2. Enter the length, width, and depth (or diameter and height for columns) in your preferred units. 3. Set the waste factor percentage to account for spillage and form irregularities, typically 10%. 4. Review the total volume in cubic yards or cubic meters, plus the estimated number of pre-mixed bags for smaller jobs. 5. Copy the results or adjust dimensions to compare different project sizes and material requirements.

About This Tool

Ordering the right amount of concrete is critical for any construction project. Too little means costly delays and cold joints, while too much means wasted material and money. This concrete calculator takes the guesswork out of the equation by computing the exact volume of concrete you need for slabs, footings, columns, and other common shapes based on your measurements.

The calculator supports multiple shape types including rectangular slabs, circular columns, and trapezoidal footings. Enter your dimensions in either imperial or metric units and get results in cubic yards or cubic meters - the two standard ordering units for ready-mix concrete. An optional 10% waste factor accounts for spillage, over-excavation, and form irregularities that are unavoidable on real job sites.

Beyond volume, the tool estimates the number of pre-mixed bags needed for smaller jobs (60 lb, 80 lb, or 90 lb bags) and provides a rough cost estimate based on typical pricing. Whether you are pouring a backyard patio, setting fence posts, or planning a foundation, this calculator helps you order confidently and avoid expensive mistakes.

Formula / How It Works

Volume = Length x Width x Thickness | Cubic Yards = Volume (ft^3) / 27 | With waste: Total = Volume x (1 + waste%)

Frequently Asked Questions

Multiply the length by the width by the thickness of the slab, all in the same units. For cubic yards, measure in feet and divide the result by 27 (since there are 27 cubic feet in a cubic yard). For example, a 10 ft x 12 ft slab that is 4 inches thick needs (10 x 12 x 0.333) / 27 = approximately 1.48 cubic yards.
A common rule of thumb is to order 10% more concrete than calculated. This accounts for spillage, slight variations in form dimensions, uneven subgrade, and the concrete left in the truck chute. For complex pours with many forms or irregular shapes, you may want to add up to 15%.
A cubic yard equals 27 cubic feet (3 ft x 3 ft x 3 ft), while a cubic meter equals 35.31 cubic feet (approximately 1.31 cubic yards). In the United States, concrete is typically ordered in cubic yards. In most other countries, cubic meters are the standard unit. This calculator supports both.
An 80 lb (36 kg) bag of pre-mixed concrete yields approximately 0.6 cubic feet when mixed. For one cubic yard, you would need about 45 bags. For a small project like a 4 ft x 4 ft slab at 4 inches thick, you need about 0.20 cubic yards or roughly 9 bags of 80 lb mix.
Standard residential slabs like patios and walkways are typically 4 inches thick. Garage floors and driveways that support vehicle traffic should be at least 5 to 6 inches thick. Heavy-duty commercial or industrial slabs may require 6 to 8 inches or more, depending on the load and soil conditions.

Related Tools

Volume Converter

Convert between liters, gallons, fluid ounces, milliliters, cups, tablespoons, teaspoons, pints, and quarts.

Unit Converters

Area Converter

Convert between square feet, square meters, acres, hectares, square kilometers, and square miles.

Unit Converters

Length Converter

Convert between meters, feet, inches, centimeters, kilometers, miles, yards, and nautical miles instantly.

Unit Converters

Paint Calculator

Estimate gallons or liters of paint needed per room based on wall dimensions, coats, and door or window deductions.

Construction and Home

Tile Calculator

Calculate the number of tiles needed for any floor or wall area, accounting for grout gaps and waste percentage.

Construction and Home

Fence Calculator

Estimate the number of posts, rails, pickets, and hardware needed for a fence based on perimeter and height.

Construction and Home