Concrete Calculator

The concrete calculator finds the volume, weight, and cost of concrete for slabs, driveways, columns, round footings, cylinders, tubes, walls, and stairs. Selecting a shape sets which dimensions and formula apply, and the result reports volume alongside a bag count for standard premixed bags.

• Shape. Slab/Driveway, Column/Round Footing, Cylinder/Tube, Wall, or Stairs, each with its own set of dimension fields and formula.
• Unit system. Imperial mode works in feet and inches, metric mode in meters and centimeters. All fields accept decimals (0.75), fractions (3/4), and mixed numbers (5 1/2).
• Waste factor. A percentage buffer added to every estimate to account for spillage, uneven surfaces, and over-excavation, so an order based on the raw geometric volume is not short on site.

Slab volume is length multiplied by width multiplied by depth. Column volume is pi multiplied by (diameter divided by 2) squared, multiplied by height and by quantity, for multiple identical posts or footings in one entry. Cylinder or tube volume subtracts the inner volume from the outer volume: pi multiplied by ((outer diameter / 2) squared minus (inner diameter / 2) squared), multiplied by height, which accounts for the hollow center of a sonotube or pipe form. Wall volume is length multiplied by height multiplied by thickness. Stairs volume sums each step as a rectangular prism, plus the platform volume. Volume converts to cubic feet, cubic yards, or cubic meters depending on the unit system, and bag counts for 40, 60, and 80 pound premixed bags round up to the nearest whole bag, since a partial bag still has to be bought. Settings holds the cost per cubic yard or cubic meter, the concrete density used for the weight estimate, the waste factor percentage, and a step-by-step breakdown of the formula, unit conversions, and waste adjustment for the selected shape.

A 10 by 10 foot slab poured 4 inches (0.33 feet) deep has a volume of 10 multiplied by 10 multiplied by 0.33, or about 33 cubic feet. Divided by 27 cubic feet per cubic yard, that is roughly 1.2 cubic yards of concrete before any waste factor is added.

This calculator serves a wide range of construction and home improvement projects where accurate concrete estimation prevents waste and cost overruns.

• Driveway Construction: A new driveway's length, width, and thickness determine total concrete volume and the number of premixed bags or ready-mix truckloads required.
• Patio and Slab Work: Backyard patios, garage floors, shed foundations, and basketball courts share the same slab formula, with material needs following directly from the slab dimensions.
• Fence Post Footings: The column shape estimates concrete for multiple fence post holes at once: hole diameter, depth, and post count give a total volume and bag count.
• Deck Footings: Round pier footings supporting a deck structure size out from a diameter and depth matched to local building codes.
• Retaining Walls: Wall length, height, and thickness estimate material for poured concrete retaining walls or foundation walls.
• Stair Construction: Front porch stairs, basement entry steps, or landscape stairs size out from rise, run, width, and number of risers.
• Budget Planning: The cost per cubic yard in settings adjusts to local material prices for an accurate cost estimate before purchasing.
• Contractor Estimation: Quick material quotes for clients follow from project dimensions, with the waste factor included to ensure sufficient material on site.
• Sonotube Projects: The cylinder shape calculates concrete for round form tubes used in pier and column construction, accounting for the hollow center.
• Sidewalk and Pathway Slabs: A standard 4-inch depth over a sidewalk's length and width, with the waste factor compensating for form irregularities and ground settlement along the path.
• Garage Floor Replacement: A new garage floor sizes from its full slab dimensions, with thickness adjusted for expected vehicle weight and local building requirements.