Concrete Calculator
Slab, Footing, Column, Walls, Stairs & Bag Calculator
Get instant, accurate concrete estimates for slabs, footings, columns, walls, stairs & more — trusted by engineers and contractors worldwide.
Bag Yield Reference
| Bag Size | Yield (ft³) | Yield (yd³) | Bags per yd³ | Coverage @ 4″ thick (ft²) |
|---|---|---|---|---|
| 40 lb | 0.30 | 0.011 | 90 | ~1.1 ft² |
| 50 lb | 0.375 | 0.0139 | 72 | ~1.4 ft² |
| 60 lb | 0.45 | 0.0167 | 60 | ~1.7 ft² |
| 80 lb | 0.60 | 0.0222 | 45 | ~2.2 ft² |
Common Sonotube Sizes — Volume per Linear Foot
| Diameter | ft³ / ft depth | yd³ / ft depth | 80 lb Bags / ft |
|---|---|---|---|
| 6 in | 0.196 | 0.0073 | 0.33 |
| 8 in | 0.349 | 0.0129 | 0.58 |
| 10 in | 0.545 | 0.0202 | 0.91 |
| 12 in | 0.785 | 0.0291 | 1.31 |
| 14 in | 1.069 | 0.0396 | 1.78 |
| 16 in | 1.396 | 0.0517 | 2.33 |
How Our Concrete Calculator Works
Engineer-verified formulas used by professionals worldwide
Enter Dimensions
Input length, width, and depth/thickness of your concrete project in feet/inches or metric units.
We Calculate Volume
Our calculator uses ACI-standard formulas to compute the exact cubic volume of concrete required.
Get Bag Count
We automatically convert volume to the number of 40, 60 or 80 lb bags you need to purchase.
Order with Confidence
Results include a 10% waste buffer recommendation, so you never run short on a pour day.
Concrete Reference Tables
Expert data for accurate project planning
| Application | Min. Thickness | Recommended | PSI Strength |
|---|---|---|---|
| Sidewalk / Walkway | 3.5 in (89 mm) | 4 in (100 mm) | 3,000–3,500 PSI |
| Residential Patio | 3.5 in (89 mm) | 4 in (100 mm) | 3,000–3,500 PSI |
| Driveway | 4 in (100 mm) | 5–6 in (125–150 mm) | 4,000 PSI |
| Garage Floor | 4 in (100 mm) | 5–6 in (125–150 mm) | 4,000 PSI |
| Basement Floor | 3.5 in (89 mm) | 4 in (100 mm) | 3,500–4,000 PSI |
| Commercial Floor | 5 in (125 mm) | 6 in (150 mm) | 4,000–5,000 PSI |
| Heavy Equipment Slab | 6 in (150 mm) | 8 in (200 mm) | 4,500–5,000 PSI |
| Measurement | Weight / Value | Notes |
|---|---|---|
| 1 cubic yard (yd³) | ≈ 4,050 lbs (1.84 tonnes) | Standard 3,000 PSI mix |
| 1 cubic foot (ft³) | ≈ 150 lbs (68 kg) | Varies with mix design |
| 1 cubic meter (m³) | ≈ 2,400 kg (2.4 tonnes) | Normal weight concrete |
| Ready-mix truck | 8–10 yd³ per load | Typical drum truck capacity |
| Ready-mix average cost | $125–$175 per yd³ | Varies by region & mix |
| Pump surcharge | +$15–$25 per yd³ | When pump truck is needed |
Pro Tips From Engineers
Best practices for every concrete project
Always Order 5–10% Extra
Account for spillage, subgrade irregularities, and over-excavation. Running short on pour day is costly.
Temperature Matters
Don’t pour concrete below 40°F (4°C) or above 90°F (32°C) without special precautions. Cure time doubles in cold weather.
Control Water-Cement Ratio
Keep w/c ratio between 0.40–0.55. Adding extra water reduces strength significantly — every 1 gallon per yd³ reduces strength ~200 PSI.
Use Control Joints
Saw-cut or form control joints every 8–12 ft in slabs to control cracking. Joints should be ¼ the slab depth.
Prepare Your Subbase
Compact granular fill to 95% proctor density. A 4″ compacted gravel base prevents slab settlement and cracking.
Cure Properly
Keep concrete moist for at least 7 days. Use curing compound, wet burlap, or plastic sheeting. Concrete reaches full strength at 28 days.
Frequently Asked Questions
Most asked questions about concrete calculators, mixes & projects
About Our Concrete Calculator
ConcreteCalculatorz.com provides the most comprehensive collection of free concrete calculators on the internet. Whether you’re a homeowner planning a backyard patio, a contractor bidding a driveway, or an engineer designing a foundation, our calculators give you fast and accurate results based on industry-standard ACI (American Concrete Institute) formulas.
All results are provided in both Imperial (cubic yards, cubic feet, bags) and Metric (cubic meters, liters) units. Our calculators cover every common pour type: concrete slabs, footings, round columns, walls, stairs, curb & gutter, sonotubes, and more — plus a universal concrete volume converter.
Every calculator includes a waste factor recommendation and bag count conversions for 40 lb, 60 lb, and 80 lb premix bags. Our reference tables and pro tips are sourced from ACI 318, IRC 2021, and practicing structural engineers to ensure you get code-compliant results every time.