Concrete Calculator
Calculate exactly how much concrete you need for slabs, footings, columns, and stairs. Get estimates in cubic yards, bags, or ready-mix truck loads.
Project Type
Slab Dimensions
4" for patios, 6" for driveways
Your Results Will Appear Here
Choose a project type, enter your dimensions, then click “Calculate” to see how much concrete you need.
Top-Rated Concrete Mix & Tools
Hand-picked products to help you get the best results on your project.
Quikrete
Quikrete Concrete Mix, 80 lb Bag
- ✓80 lb bag = 0.6 cu ft
- ✓All-purpose mix
- ✓Sets in 24 hours
Sakrete
Sakrete High-Strength Concrete Mix, 80 lb
- ✓5,000 PSI strength
- ✓Structural grade
- ✓Meets ASTM standards
Quikrete
Quikrete Fast-Setting Concrete Mix, 50 lb
- ✓Sets in 20-40 min
- ✓No mixing needed
- ✓Perfect for posts
Bon Tool
Bon Tool Concrete Mixing Hoe, 10 Inch
- ✓10-inch blade
- ✓Mortar holes for mixing
- ✓Steel construction
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How to Use This Concrete Calculator
Step 1: Choose Project Type
Select from slab, footing, column/post hole, or stairs. Each type uses different dimensions and formulas.
Step 2: Enter Dimensions
Enter your project’s length, width, and thickness (or diameter and height for columns). Use feet for length and inches for thickness.
Step 3: Review Settings
Our calculator adds 10% waste automatically. This accounts for spillage, uneven ground, and overpouring.
Step 4: Compare Options
See both bag counts (80 lb and 60 lb) and ready-mix truck loads. Compare costs to choose the best option for your project size.
Step 5: Get Results
Click Calculate to see cubic yards, bag counts, truck loads, and cost comparison for bags vs. ready-mix delivery.
Understanding Concrete
Slab Thickness Guide
| Project | Thickness | Notes |
|---|---|---|
| Patio | 4" | Foot traffic only |
| Sidewalk | 4" | Residential standard |
| Driveway | 6" | Vehicle traffic |
| Garage Floor | 6" | Heavy loads |
Bags vs. Ready-Mix
Bags (60\u201380 lb): Best for small projects under 1 cubic yard. Mix in a wheelbarrow or mixer. Each 80 lb bag yields about 0.6 cubic feet. Ready-mix delivery: Best for projects over 1 cubic yard. Arrives pre-mixed in a truck. Minimum order is usually 1 cubic yard. Significantly less labor than mixing bags.
Curing Best Practices
Proper curing is critical for concrete strength. Keep the surface moist for at least 7 days by misting with water or covering with plastic sheeting. Avoid walking on fresh concrete for 24–48 hours. Full strength develops at 28 days. Never pour concrete below 40°F.
Pro Tips for Concrete Projects
Consider Ready-Mix for Projects Over 1 Cubic Yard
Mixing 45+ bags of concrete by hand is exhausting and time-consuming. Ready-mix delivery costs about $125–$150 per cubic yard and saves hours of labor. Most companies have a 1-yard minimum order.
Standard Slab Thickness: 4” Patios, 6” Driveways
Don’t guess on slab thickness. Patios and walkways need 4 inches minimum. Driveways and garage floors need 6 inches to handle vehicle weight without cracking.
Add Wire Mesh or Rebar for Large Slabs
For slabs larger than 8×8 feet, add welded wire mesh or rebar reinforcement. This prevents cracks from spreading and significantly increases the slab’s lifespan. Place reinforcement at the middle of the slab’s thickness.
Don’t Add Too Much Water
Excess water makes concrete easier to pour but dramatically weakens the final product. Mix to a thick, workable consistency—like thick oatmeal. If the mix is too dry, add water tablespoon by tablespoon.
Cure Slowly by Keeping Concrete Moist
Fast drying creates weak, crumbly concrete. Cover with plastic sheeting or mist with water several times a day for 7 days. The slower concrete cures, the stronger it becomes. Avoid direct sunlight on fresh pours.
Frequently Asked Questions
A 10×10 foot slab at 4 inches thick needs about 1.23 cubic yards of concrete, or roughly 1.36 cubic yards with 10% waste. That’s about 62 bags of 80 lb concrete mix. For a project this size, consider ordering ready-mix delivery instead of mixing bags.
Use bags for small projects under 1 cubic yard (about 45 bags of 80 lb mix). For anything larger, ready-mix delivery is more practical and often cheaper. Mixing 45+ bags by hand is exhausting and takes hours. Ready-mix arrives pre-mixed and ready to pour.
Standard thicknesses: 4 inches for patios, walkways, and shed floors; 6 inches for driveways and areas with vehicle traffic; 4 inches for sidewalks. Heavy equipment areas may need 8+ inches. Thicker slabs resist cracking but use significantly more concrete.
One cubic yard of concrete requires approximately 45 bags of 80 lb concrete mix (each bag yields about 0.6 cubic feet, and 1 cubic yard = 27 cubic feet). At roughly $7 per bag, that’s about $315 per cubic yard in bags, compared to $125–$150 for ready-mix delivery.
You can walk on concrete after 24–48 hours. Light vehicle traffic is safe after 7 days. Full strength (typically 4,000 PSI) is reached at 28 days. During curing, keep concrete moist by misting with water or covering with plastic. Avoid freezing temperatures during the first 48 hours.
Don’t pour concrete when temperatures are below 40°F or expected to drop below freezing within 24 hours. Cold weather slows curing and can cause the surface to freeze before setting, creating a weak, crumbly finish. Use cold-weather concrete mix and insulating blankets if you must pour in cool conditions.