Concrete Calculator

Estimate concrete volume and the number of bags needed for your project.

Mix Estimator

Professional grade concrete volume and bag calculator.

Length (ft)

Width (ft)

Thickness (in)

80lb Bag Estimate0 Bags

60lb Bag Estimate0 Bags

Visual Plan

Relative Dimensions Preview

Enter Dimensions

Pro Insight

Always order 10% more concrete than calculated to account for spillage, waste, and subgrade inconsistencies.

Understanding the Concrete Calculator

Accurately estimate the amount of concrete needed for slabs, footings, columns, and tubes. Whether you are pouring a driveway, patio, or setting fence posts, our tool helps you buy the right amount of premix bags or bulk ready-mix.

Guide

How to use the Concrete Calculator

1Select your project type: 'Slabs / Footings' (rectangular) or 'Tubes / Posts' (cylindrical).
2Enter the dimensions (Length, Width, Thickness or Diameter, Depth).
3Specify the quantity if you have multiple identical items (e.g., 10 post holes).
4Review the calculated volume in Cubic Yards and the estimated number of 60lb or 80lb bags required.
5Use the 'Pro Insight' tips to adjust for waste.

Applications

Common Use Cases

Driveways & Patios: Calculate slab volume for large flatwork.

Fence Posts & Deck Piers: Estimate concrete for Sono tubes.

Retaining Wall Footings: Determine material needs for structural foundations.

Sidewalks: Plan quantity for walkways and paths.

The Maths Behind the Calculation

Volume (cy) = (Length × Width × Thickness) / 27

We first calculate the volume in cubic feet (ft³) and then divide by 27 to convert to Cubic Yards (yd³), which is the standard unit for ordering ready-mix concrete. For bags, we divide the volume by the yield of a standard bag.

Knowledge Base

Frequently Asked Questions

How many bags of concrete make a yard?

It typically takes about 45 bags of 60lb mix or 33-34 bags of 80lb mix to equal one cubic yard of concrete.

How thick should a concrete slab be?

Standard walkways and patios are usually 4 inches thick. Driveways or areas supporting heavy vehicles should be at least 5-6 inches thick with reinforcement.

Do I need to add extra for waste?

Yes, it is standard practice to add 5-10% extra to your order to account for uneven subgrade, spillage, and settling.

What is the difference between 3000 psi and 4000 psi concrete?

PSI refers to the compressive strength. 3000-3500 psi is standard for residential slabs, while 4000+ psi is used for heavy-duty applications or colder climates to resist freeze-thaw cycles.

Regional Notice: United States

"Federal tax estimates are based on 2024 brackets. Consult a tax professional for official filing."

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