Concrete Calculator
ConstructionCalculate how many bags of concrete you need for driveways, patios, slabs, and any concrete project. Enter dimensions, shape, and bag size to get instant results including cost estimates.
Dimensions
Concrete Settings
Results
Concrete Coverage by Depth (per Cubic Yard)
| Depth | Square Feet (1 yd³) | 80-lb Bags | 60-lb Bags |
|---|---|---|---|
| 2 inches | 162 sq ft | 20 bags | 27 bags |
| 3 inches | 108 sq ft | 30 bags | 40 bags |
| 4 inches | 81 sq ft | 40 bags | 54 bags |
| 5 inches | 65 sq ft | 51 bags | 68 bags |
| 6 inches | 54 sq ft | 60 bags | 81 bags |
| 8 inches | 41 sq ft | 81 bags | 108 bags |
* 1 cubic yard = 27 cubic feet. Actual bags may vary based on bag weight and waste percentage.
Concrete Mix Types & Typical Applications
| Mix Type | Strength (psi) | Best For | Typical Cost |
|---|---|---|---|
| Standard (4000 psi) | 4000 | Driveways, patios, slabs | $3.50-$5/bag |
| High Strength (5000 psi) | 5000 | Heavy traffic, foundations | $4.50-$6/bag |
| Fiber Reinforced | 4000 | Reduces cracking, non-structural | $4-$5.50/bag |
| Self-Consolidating | 4000 | Easy pour, complex shapes | $6-$8/bag |
| Air-Entrained | 4000 | Freeze-thaw resistance (cold climates) | $4-$5.50/bag |
Frequently Asked Questions
How many bags of concrete do I need for my project?
To calculate bags needed: (1) Measure your area in square feet (length × width). (2) Decide on concrete depth in inches (typical: 4-6 inches for driveways, 3-4 for patios). (3) Use the formula: Area (sq ft) × Depth (inches) ÷ 324 = cubic yards. (4) Multiply cubic yards by 60 (for 80-lb bags) or 54 (for 60-lb bags). Our calculator does this instantly and adds waste allowance (typically 5-15%).
What concrete depth should I use?
Typical depths: Driveways: 4-6 inches (4 inches minimum, 6 if heavy traffic). Patios: 3-4 inches (4 inches for durability). Walkways: 3-4 inches. Footings: 12+ inches. Garden beds: 2-3 inches. Garage floors: 4-6 inches. Add ½-1 inch extra for grading and settling. Use the depths that match your project type.
Should I use 60-lb or 80-lb concrete bags?
60-lb bags are easier to handle and pour for DIY projects. 80-lb bags are more economical (fewer bags = less material waste). For 1 cubic yard: 60-lb bags ≈ 54 bags, 80-lb bags ≈ 40 bags. Choose 80-lb for cost savings if you can handle the weight, or 60-lb for ease (especially for projects over a few cubic yards).
What is waste percentage in concrete calculations?
Waste (5-15%) accounts for spillage, settling, and uneven surfaces. Use: 5% if experienced and grading is flat. 10% for standard DIY projects (most common). 15% for irregular shapes, poor grading, or inexperienced pouring. Always round up to whole bags—you can't order 43.5 bags. It's better to have extra concrete than to run short mid-pour.
How long does concrete take to cure before I can use it?
Concrete reaches 70% strength in 7 days and 95% strength in 28 days. Timing: Light foot traffic (walking): 24-48 hours. Vehicle traffic on driveway: 7 days minimum. Full strength and ready for heavy use: 28 days. Weather affects curing—cold delays it, heat speeds it up. Keep concrete moist during curing for best results.
Can I calculate concrete for circular or irregular areas?
Yes! For circles: Use πr² to get square footage, then enter that in the calculator's irregular shape option. For irregular shapes: Break it into rectangles/circles, calculate each separately, then add the results. Or estimate the total area and use the irregular shape option. Our calculator supports both rectangular and circular measurements.
How much does a cubic yard of concrete cost?
Ready-mix concrete (delivered): $150-250 per cubic yard depending on location and mix (air-entrained, fiber-reinforced, etc.). Bagged concrete (DIY): $3.50-$8 per bag (80-lb), or $5.40-$12.30 per cubic yard depending on bag size and location. Ready-mix is cheaper for large projects (5+ cubic yards), bags are better for small projects. Prices vary by region and supplier.