Concrete Calculator

How to Calculate Concrete for Your Next Project

Whether you are pouring a new patio, setting fence posts, pouring stairs, or building a custom structural shape, ordering the right amount of concrete is crucial. Ordering too much wastes money, while ordering too little creates a stressful, interrupted pour. Our Concrete Calculator is highly flexible, supporting multiple units (feet, inches, yards, meters, and centimeters) and complex shapes.

1. Calculating Concrete for Slabs and Rectangles

For standard rectangular structures like driveways, sidewalks, and slabs, you need to determine the volume of a rectangular prism. Simply enter your length, width, and depth.

Volume = Length × Width × Depth

2. Calculating Concrete for Columns and Post Holes

When setting deck posts or pouring sonotube columns, you are calculating the volume of a cylinder. The calculator automatically finds the area of your circular base based on the diameter, and multiplies it by the depth of your hole.

Where V is Volume, r is the radius (half the diameter), and h is the height or depth.

3. Calculating Concrete for Stairs

Figuring out the concrete requirement for stairs can be tricky. Our calculator simplifies this by calculating the volume of each step as a rectangular prism. You will need:

• Tread Depth: The horizontal part of the step you step on.
• Riser Height: The vertical height of a single step.
• Width: The side-to-side width of the staircase.
• Number of Steps: The total amount of stairs to be poured.

4. Estimating Premixed Concrete Bags

For smaller projects, buying premixed bags (like Quikrete or Sakrete) is highly cost-effective. Premixed bags are sold by weight but yield standard volumes when mixed with water:

• 80 lb bag: Yields roughly 0.60 cubic feet of concrete.
• 60 lb bag: Yields roughly 0.45 cubic feet of concrete.
• 50 lb bag: Yields roughly 0.37 cubic feet of concrete.

Note: Our calculator automatically rounds up to the nearest whole bag so you are never left short!

Pro Tip: The Rule of Waste

In construction, things rarely go perfectly. Ground isn't perfectly level, wooden forms bulge, and spillage is inevitable. It is an industry standard to order an extra 5% to 10% of your calculated concrete to account for waste. It is significantly cheaper to have half a yard leftover than to pay short-load fees for an extra truck delivery!