Math Calculators
Concrete Volume Calculator
Concrete volume depends on the shape and dimensions of the pour: length × width × depth for slabs and rectangular columns, or π × radius² × height for a cylinder. Enter the yield printed on the concrete bag to estimate how many bags are needed. Choose units that match your measurements; fractional bag results are rounded up, with no added waste margin.
Calculator
Formula and sources
A slab uses V = L × W × H. A cylinder uses V = πr²h. Bags = ceiling(volume ÷ stated yield). Dimensions and yield must be positive. No extra material allowance is included. Formula reference: OpenStax, Contemporary Mathematics §10.7, https://openstax.org/books/contemporary-mathematics/pages/10-7-volume-and-surface-area. Inch = exactly 25.4 mm and foot = exactly 0.3048 m (NIST, https://www.nist.gov/pml/owm/si-units-length).
About This Calculator
What It Does
This tool estimates geometric concrete volume for three common pour shapes: a slab, a rectangular column and a cylinder. It converts dimensions to cubic metres, then translates the volume into the selected bag-yield unit. Enter the yield shown by the manufacturer; it is not assumed from bag weight.
Worked Example
Example — A 4 m × 3 m × 0.10 m slab is 1.2 m³. At the metric default yield of 20 L per bag, 1.2 ÷ 0.020 = 60 bags. Fractional results round up; no waste allowance is added.
Real-World Usage
Use this estimate to plan a slab, rectangular pier or cylindrical footing. Check actual dimensions and the yield on the product package. Site conditions and placement losses are outside the calculation.
Local Context
Metric dimensions are the default except on US pages, which start in feet. Dimension and bag-yield units can be changed independently. This geometric estimate does not guarantee the quantity to purchase.
Last reviewed: October 2026.
Frequently Asked Questions
How are bags calculated?
The volume is divided by the stated yield per bag and rounded up. No waste allowance is included.
How much concrete do I need for a slab?
Enter the slab length, width and thickness and the calculator returns the volume in cubic metres, cubic feet and litres, together with the whole number of bags your stated yield requires.
Does this calculator include waste or compaction?
No. The result is the exact geometric volume of the shape you entered, so add your own margin for spillage, compaction and uneven ground before you order.
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