🧱 Concrete Calculator
ft
ft
in
Results
Volume33.3 ft³
Cubic yards1.23 yd³
60-lb bags≈75 bags
80-lb bags≈56 bags
⚠️Estimate — bag yield varies with mixing. Volume calculation is exact for rectangular slabs.
How to Use This Calculator
Calculate how much concrete you need for a slab, walkway, or foundation. Enter the length, width, and depth to get the volume in cubic yards and the number of bags required.
- Measure the length and width of your slab in feet.
- Measure the depth (thickness) in feet or inches.
- The calculator converts all dimensions to cubic feet, then to cubic yards.
- Choose between 60 lb bags (0.45 cu ft each) or 80 lb bags (0.6 cu ft each).
- Read the total volume and bag count.
How the Calculation Works
Volume in cubic feet = length × width × depth. Divide by 27 to convert to cubic yards. For bags: divide total cubic feet by the yield per bag (0.45 for 60 lb, 0.6 for 80 lb).
Example
A 10 ft by 12 ft patio slab at 4 inches thick: volume is 10 × 12 × 0.333 = 40 cubic feet = 1.48 cubic yards. That requires about 67 bags of 80 lb concrete mix.
Pro Tips
- Always order 5-10% more concrete than calculated to account for uneven ground and spillage.
- For slabs thicker than 4 inches, consider ordering ready-mix concrete delivery instead of bags.
- Standard slab thickness is 4 inches for patios and walkways, 6 inches for driveways.
- Reinforce slabs with wire mesh or rebar for driveways and heavy-load areas.
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