A clear result in a few inputs.
- Enter the requested values.Use consistent units and the real values for your scenario.
- Read the main result and breakdown.NumLuma recalculates immediately when an input changes.
- Check the formula and assumptions.Use the supporting context before making a real-world decision.
What this calculator does
Concrete is ordered by volume, so depth matters just as much as length and width. The calculator converts slab depth from inches to feet, computes cubic feet, converts that amount to cubic yards, and then applies the allowance you choose.
What to know before you use the result
- Use average finished depth if the base is not perfectly uniform.
- One cubic yard equals 27 cubic feet.
- Delivery minimums, site conditions and supplier rounding can change the amount you actually order.
Common mistakes to avoid
- Entering slab depth in inches as though it were feet.
- Using the outside form dimensions when the actual poured dimensions are different.
- Ignoring uneven excavation or subgrade variation.