Calc4Living

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Concrete Calculator

Estimate material volume for a rectangular slab or solid cylindrical form, with waste and optional bags based on stated mixed-concrete yield.

Your project inputs

Prefilled measurements and product coverage are editable examples, not product or structural recommendations. All fields are required unless marked optional.

Changing units converts current measurements, product coverage and price per area. Results clear when any input changes.

Yield is mixed concrete volume per bag, never bag weight.

Measured dimension in the selected unit.

Measured dimension in the selected unit.

Uniform internal fill depth; dimensions are not structural recommendations.

Optional extra material added to the estimate. Blank or 0 means no allowance.

Enter manufacturer mixed volume per bag. Bag weight in kg/lb is not yield. Greater than zero.

Your estimate

Materials & purchasing quantities

Review the example values, enter your measurements and product specifications, then calculate. Results clear whenever inputs change.

How much concrete do I need for a slab or cylindrical form?

Slab volume = length × width × thickness. Solid cylinder volume = π × (diameter/2)² × height. Order volume = geometric volume × (1 + waste/100). Bags = ceiling(order volume ÷ manufacturer mixed-concrete yield per bag).

Worked example

A 4 m × 3 m slab, 10 cm thick, has a geometric volume of 1.2 m³. Adding 10% gives 1.32 m³ (about 1.7265 yd³). If a bag yields 12 L of mixed concrete, ceiling(1.32 ÷ 0.012) = 110 bags. The 12 L yield is an editable example, not a bag-weight conversion.

Unit conversions

1 ft = 0.3048 m; 1 in = 0.0254 m; 1 cm = 0.01 m. Area conversions use squared length factors, and volume conversions use cubed factors. 1 yd³ = 27 ft³ = 0.764554857984 m³; 1 L = 0.001 m³.

Assumptions & limitations

  • Uses internal form dimensions and a uniform thickness or solid cylinder height. Hollow tubes, complex footings, slopes and irregular excavation are not included.
  • Use the actual mixed yield on the bag or supplier datasheet, not the bag weight in kg or lb. Different products and mixing conditions produce different yields. No density-based weight-to-volume assumption is made.
  • Waste is extra volume added for placement and dimensional variation. Strength, reinforcement, loads, foundations, curing and structural suitability require professional assessment; this tool estimates material quantities only.