MathUpdated December 2025

Concrete Calculator

Calculate concrete volume in cubic feet and cubic yards, plus weight and 60 lb / 80 lb bag counts, for slabs, footings, columns, and circular pours.

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Updated 2025
Concrete Calculator
Use this free concrete calculator to estimate concrete volume, cubic yards, and 60 lb / 80 lb bag counts for slabs, footings, and circular pours.
Slab, Square Footing, or Wall
Enter dimensions for rectangular concrete areas
About Concrete Calculations

Concrete Mix Formula:

  • Volume Calculation: Length × Width × Thickness (for slabs)
  • Circular Volume: π × Radius² × Depth
  • Weight: Approximately 150 pounds per cubic foot
  • Bag Coverage: 60lb bag = 0.45 cubic feet, 80lb bag = 0.6 cubic feet

Pro Tips:

  • Order 5-10% extra concrete to account for spillage and uneven ground
  • Consider reinforcement (rebar) for structural integrity
  • Prepare the site properly with proper grading and compaction
  • Check weather conditions - avoid pouring in extreme temperatures

This calculator provides estimates. Actual requirements may vary based on project specifics, local conditions, and waste factors. Always consult with a professional for large projects.

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How our concrete calculator works

1

Choose your shape

Select slab, footing, column, circular tube, or stairs. Each shape uses the right volume formula: length x width x height for slabs, pi x r^2 x height for cylinders, etc.

2

Enter dimensions

Type dimensions in feet, inches, yards, meters, or centimeters. The calculator converts and rounds to the precision you need for ordering.

3

Get volume plus bag count

See the volume in cubic yards and cubic feet, the total weight, and the number of 60 lb or 80 lb bags to buy. We add a 5-10% waste factor so you order enough.

Key things to know about our concrete calculator:

  • Most orders quote by the cubic yard: 1 cubic yard = 27 cubic feet. Most concrete trucks hold 8-10 cubic yards minimum, so plan a single pour to save delivery fees.
  • Bag vs ready-mix: Under 1 cubic yard, bags are economical. Over 1 cubic yard, ready-mix delivery is usually cheaper per cubic foot and saves hours of mixing.
  • Reinforcement: Concrete is strong in compression but weak in tension. Add rebar or wire mesh for slabs, driveways, and any load-bearing application.

For related calculations, try our square footage calculator.

FAQ

Frequently asked questions

Everything you need to know about this calculator. Can't find what you're looking for? Email our team.

One cubic yard of concrete equals about 45 80-lb bags, 60 60-lb bags, or 90 40-lb bags. Our concrete calculator shows all three bag sizes in the result. For most DIY projects under 1 cubic yard, bags are cheaper than ready-mix delivery. The concrete calculator adds 10% to your result for waste and uneven subgrade.

How it works

How to estimate concrete volume and bag count

Our concrete calculator lets you calculate cubic yards, cubic feet, weight, and bag counts for slabs, footings, columns, and circular pours, in three steps.

  1. 1

    Pick the shape and enter dimensions

    Select Slab/Square for rectangular pours (patios, driveways, footings) or Circular for round forms (tube footings, sonotubes, round pads). Enter the length, width, and thickness in feet and inches, or diameter and depth for circles. Set quantity if you are pouring multiple identical slabs.

  2. 2

    Click Calculate Concrete

    Press the Calculate Concrete button. The result shows volume in cubic feet and cubic yards, total weight in pounds, and the number of 60 lb and 80 lb bags needed. Add 10% to the result for waste and uneven subgrade.

  3. 3

    Order and pour

    Use cubic yards to order ready-mix (typical truck holds 8-10 yards), or buy 60 lb / 80 lb bags for small jobs. Concrete weight is ~150 lb per cubic foot. Order on a cool morning and pour within 90 minutes of mixing for the best finish.

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