Concrete Slab Calculator
Estimate concrete volume, bags, and cost for your slab project
Length of the slab
Width of the slab
Standard: 4" for patio, 6" for driveway
Concrete Volume
—
cubic yards
Concrete Volume
—
cubic feet
60 lb Bags
—
bags
80 lb Bags
—
bags
Estimated Cost
—
USD
Disclaimer: Results are estimates based on standard formulas. Not a substitute for professional advice from a licensed contractor, engineer, or architect. Verify all calculations before making purchasing or construction decisions.
How to Use This Calculator
Planning a concrete slab project? Whether you are pouring a patio, driveway, shed floor, or foundation, getting the right amount of concrete is crucial. Our calculator helps you estimate exactly how much concrete you need.
- Measure the length and width of your slab area in feet
- Determine the required thickness (4" for patios, 6" for driveways)
- Enter your dimensions in the calculator
- Add 5-10% extra for spillage
- Order ready-mix for projects over 1 cubic yard
Expert Insights
Smart analysis for your Concrete & Masonry project
Slab Thickness Guide
4" for patios, 5-6" for driveways, 6-8" for heavy vehicle loads. Our calculator references your dimensions against ACI 301-20 standards for optimal thickness recommendations.
Bag vs Ready-Mix Analysis
For pours under 1 cubic yard, 80lb bags cost less. Over 3 yards, ready-mix saves 30-50%. Our calculator factors your volume against regional pricing.
Curing & Strength Timeline
Concrete reaches 50% strength in 3 days, 70% in 7 days, and full cure in 28 days. Cold weather? Our calculator flags when heated enclosures are needed.
Calculation Formula
Volume (cu ft) = Length x Width x (Thickness / 12)
Volume (cu yd) = Volume (cu ft) / 27
Concrete Bag Size Comparison
| Bag Size | Bags per Cu Yd | Coverage at 4" | Best For |
|---|---|---|---|
| 40 lb | ~90 bags | ~0.30 sq ft/bag | Small repairs, fence posts |
| 50 lb | ~72 bags | ~0.37 sq ft/bag | Steps, small pads |
| 60 lb | ~60 bags | ~0.45 sq ft/bag | Patios, walkways |
| 80 lb | ~45 bags | ~0.60 sq ft/bag | Driveways, large slabs |
| Ready-Mix | 1 truck load | ~81 sq ft/yard | Projects over 1 cu yd |
Authority References
Our calculations are based on guidelines and standards from these authoritative sources:
- American Concrete Institute (ACI) — ACI 301-20 — Specifications for Structural Concrete. Learn more
- Portland Cement Association (PCA) — Concrete Slab Thickness Guidelines. Learn more
- Quikrete — Concrete Calculator & Mix Guidelines. Learn more
- NRMCA — Concrete in Practice (CIP) Series. Learn more
Frequently Asked Questions
How many bags of concrete do I need for a 10x10 slab?
For a 10x10 slab at 4 inches thick, you need approximately 56 bags of 80lb concrete or 75 bags of 60lb concrete, about 1.23 cubic yards.
How thick should a concrete slab be?
Standard: 4 inches for patios and walkways, 5-6 inches for driveways, 6-8 inches for heavy loads.
How much does a concrete slab cost?
Average cost is $4-$8 per square foot installed, or $110-$165 per cubic yard for ready-mix. A 10x10 slab typically costs $400-$800.
Should I order ready-mix or use bags?
For projects over 1 cubic yard, ready-mix is usually more cost-effective. For smaller projects, bagged concrete is more practical.