Concrete Calculators

Concrete is ordered by the cubic yard and sold in bags by the cubic foot, so almost every concrete job starts with the volume of the form. The tools here work out the volume for slabs, columns, steps and driveways and turn it into bags or yards, with an allowance for waste.

Which tool answers which question

• Concrete Bags Calculator: Convert cubic yards or cubic feet into the number of 40, 50, 60 or 80 lb concrete bags.
• Concrete Calculator: Turn slab, wall, footing or post-hole dimensions into cubic yards and 40, 60 or 80 lb bag counts.
• Concrete Column Calculator: Get cubic yards and bag counts for round tube-form or square concrete columns and piers.
• Concrete Driveway Calculator: Estimate driveway concrete in yards and truck loads, plus material and installed cost.
• Concrete Slab Calculator: Find cubic yards, bag counts and ready-mix cost for a patio, shed pad or garage slab.
• Concrete Steps Calculator: Work out cubic yards and bags for poured concrete steps, including a top landing.

Bags or ready-mix

For small jobs, bagged concrete is convenient, though you are mixing, hauling and lifting every bag. A common rule is that jobs much over one cubic yard are better ordered as ready-mix, which arrives mixed and is placed before it begins to set. Ready-mix is priced by the cubic yard with a minimum, so compare the cost and the labor.

Preparing, pouring and curing

A good slab depends on a compacted, level base, the right thickness and reinforcement, and proper curing. Concrete gains strength as it cures, and drying too fast in heat, wind or sun weakens the surface, so keep it moist and protected. Cold weather and rain need special care. Wear gloves, eye protection and waterproof boots, because wet concrete burns skin.

Common mistakes

• Skipping the waste allowance. Uneven ground and spills use more than the form's volume.
• Using the wrong thickness. Check what your application and local code call for.
• Letting it dry too fast. Cure the slab and keep it moist.
• Ordering too late. Ready-mix has a window to place and finish.