Concrete Calculator for Slabs, Stairs, Columns, Piers

If you're planning a construction project, knowing how much concrete you need is crucial. Our Concrete Calculator simplifies the process by providing accurate estimates for slabs, columns, curbs, and stairs. Whether you're pouring a patio, installing a curb, or building steps, this calculator helps you determine the exact number of concrete bags required—saving you time, money, and unnecessary waste.

Based on 5,000+ reviews from

Concrete Bag Calculator

Shape Image

How to Use the Concrete Calculator

Our free online concrete calculator allows you to estimate the volume of concrete needed and how many bags of concrete you should purchase based on your selected shape.

Step 1: Choose Your Shape

Select the type of concrete pour:


Slab – Driveways, patios, sidewalks, or foundation bases
Circular Column – Fence posts, pillars, or supports
Curb – Borders, landscaping edges, or driveway curbs
Stairs – Steps for porches, decks, or entryways

Step 2: Enter Your Dimensions

Depending on the selected shape, enter measurements such as:

  • Length, width, and thickness (for slabs)
  • Diameter and height (for circular columns)
  • Curb length, height, and thickness (for curbs)
  • Run, rise, width, and step count (for stairs)

Step 3: Select Your Concrete Bag Size

Choose from 40 lb, 60 lb, or 80 lb bags to calculate how many you'll need for your project.

Step 4: Get Your Estimate

Click "Calculate" to instantly see how many bags of concrete mix are required.

Why Use Our Concrete Calculator?

Saves Time and Effort

Skip the manual calculations and get instant results with just a few clicks.

Prevents Over-Ordering or Under-Ordering

Avoid wasting money on excess concrete or running short in the middle of your project.

Works for Multiple Project Types

Our concrete volume calculator covers a wide range of construction needs—from small residential projects to large commercial pours.

Accurate and Easy to Use

Enter your dimensions, select a bag size, and let the calculator do the math for you.

How to Calculate Concrete Volume Manually

If you prefer to calculate concrete volume yourself, use these formulas:

Formula for Slabs

📌 Volume (cubic feet) = Length (ft) × Width (ft) × Thickness (ft)

Formula for Circular Columns

📌 Volume = π × (Radius²) × Height

(π ≈ 3.1416, Radius = Diameter ÷ 2)

Formula for Curbs

📌 Volume = Length × Height × Thickness

Formula for Stairs

📌 Volume = Run × Rise × Width × Number of Steps

Once you have the volume in cubic feet, divide by bag yield per cubic foot:

  • 40 lb bag → Yields 0.30 cu ft
  • 60 lb bag → Yields 0.45 cu ft
  • 80 lb bag → Yields 0.60 cu ft

Example Calculation

A 10 ft × 4 ft × 6-inch slab has a volume of:


📌 10 × 4 × 0.5 = 20 cubic feet

If using 60 lb bags (0.45 cu ft per bag):

📌 20 ÷ 0.45 = 45 bags

Start Your Project with Accurate Concrete Estimates

Don't risk underestimating or overbuying concrete for your next project. Use our free concrete calculator to quickly determine how many bags of concrete you need—whether you're pouring a slab, setting fence posts, installing curbs, or building stairs.

👉 Try our pro concrete drawing and estimating app to simplify your construction planning!

How to Use the Concrete Calculator

Our free online concrete calculator allows you to estimate the volume of concrete needed and how many bags of concrete you should purchase based on your selected shape.

Step 1: Choose Your Shape

Select the type of concrete pour:


Slab – Driveways, patios, sidewalks, or foundation bases
Circular Column – Fence posts, pillars, or supports
Curb – Borders, landscaping edges, or driveway curbs
Stairs – Steps for porches, decks, or entryways

Step 2: Enter Your Dimensions

Depending on the selected shape, enter measurements such as:

  • Length, width, and thickness (for slabs)
  • Diameter and height (for circular columns)
  • Curb length, height, and thickness (for curbs)
  • Run, rise, width, and step count (for stairs)

Step 3: Select Your Concrete Bag Size

Choose from 40 lb, 60 lb, or 80 lb bags to calculate how many you'll need for your project.

Step 4: Get Your Estimate

Click "Calculate" to instantly see how many bags of concrete mix are required.

Why Use Our Concrete Calculator?

Saves Time and Effort

Skip the manual calculations and get instant results with just a few clicks.

Prevents Over-Ordering or Under-Ordering

Avoid wasting money on excess concrete or running short in the middle of your project.

Works for Multiple Project Types

Our concrete volume calculator covers a wide range of construction needs—from small residential projects to large commercial pours.

Accurate and Easy to Use

Enter your dimensions, select a bag size, and let the calculator do the math for you.

How to Calculate Concrete Volume Manually

If you prefer to calculate concrete volume yourself, use these formulas:

Formula for Slabs

📌 Volume (cubic feet) = Length (ft) × Width (ft) × Thickness (ft)

Formula for Circular Columns

📌 Volume = π × (Radius²) × Height

(π ≈ 3.1416, Radius = Diameter ÷ 2)

Formula for Curbs

📌 Volume = Length × Height × Thickness

Formula for Stairs

📌 Volume = Run × Rise × Width × Number of Steps

Once you have the volume in cubic feet, divide by bag yield per cubic foot:

  • 40 lb bag → Yields 0.30 cu ft
  • 60 lb bag → Yields 0.45 cu ft
  • 80 lb bag → Yields 0.60 cu ft

Example Calculation

A 10 ft × 4 ft × 6-inch slab has a volume of:


📌 10 × 4 × 0.5 = 20 cubic feet

If using 60 lb bags (0.45 cu ft per bag):

📌 20 ÷ 0.45 = 45 bags

Start Your Project with Accurate Concrete Estimates

Don't risk underestimating or overbuying concrete for your next project. Use our free concrete calculator to quickly determine how many bags of concrete you need—whether you're pouring a slab, setting fence posts, installing curbs, or building stairs.

👉 Try our pro concrete drawing and estimating app to simplify your construction planning!

Overview

Resource tags

How to Get the Free Download

Where should we send it?

You're a few seconds away from your free download!

First name *
Last name *
Email *
By submitting this form you agree with our Terms and Privacy Policy

FAQs

How do I know how many bags of concrete to buy?

Use the calculator by entering your project dimensions and selecting a bag size. The tool will estimate the exact number of bags required.

What size concrete bag should I use?

Choose a bag size based on your project needs and your ability to handle the specific weight of bags. While you need less 80lb bags compared to 40 lb bags, the difficulty to move them will be increasingly harder as you move up in size. Bags come in sizes by weight: 40 lb, 60 lb, 80 lb.

Can I use this calculator for ready-mix concrete?

Yes! While this calculator is optimized for pre-mixed concrete bags, you can use it to estimate cubic yardage for ready-mix concrete as well.