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