Purpose and steps
Area from each selected shape is multiplied by depth to get volume. Total volume is divided by bag yield and rounded up, with cubic-foot, cubic-yard, and cubic-meter conversions.
- Measure each area in consistent length units and confirm the product’s package coverage or volume yield.
- Split irregular areas into regular shapes and enter dimensions, depth or coverage. Set openings, waste and coats for the actual project.
- Check the headline result and its components. A key interpretation for this tool is: Compare the calculated cubic yards with local bulk-delivery minimums.
- Compare the baseline with a changed scenario: Use finished depth, not the loose pile height.
Model-specific method
How this calculator produces its result
Volume = bed area × depth. Bags = volume ÷ labeled bag volume, rounded up.
Volume, density and cubic unit conversions
A thin layer still has a three-dimensional volume. Multiplying square feet by inches without dividing depth by twelve overstates cubic feet by a factor of twelve. One cubic yard is three feet in each direction, hence 3³=27 cubic feet, not three cubic feet.
Converting volume into gravel mass adds a density assumption, while converting concrete volume into bags adds a product-yield assumption. Settlement, compaction, voids and moisture change these quantities. Measure finished depth and use supplier specifications; a bag’s dry weight is not interchangeable with its volume yield.
Volume V = area A × depth d Mass = V × bulk density Bags = ceil(V / yield per bag) 1 yd³ = 27 ft³
- Convert depth to the same length unit as the area dimensions
- Bulk density must match the chosen material and moisture
- Bag yield is volume after mixing when the product specifies it
- One cubic unit involves three length dimensions
Worked example
A 12 × 6 ft bed at 3 in deep needs 18 cu ft, or about 0.67 cu yd. With 2 cu ft bags, buy 9 bags before any extra allowance.
Reading results without overstating them
- Compare the calculated cubic yards with local bulk-delivery minimums.
- Use finished depth, not the loose pile height.
Assumptions and exclusions
- Settlement and uneven grade can change actual volume.
- For larger jobs, compare bags with bulk delivery.
- Settlement, existing mulch, slopes, and irregular edges affect delivered volume.
Sources and content notes
Toolify describes the implemented algorithm and its assumptions. Sources below support the topic or applicable rules; they do not endorse this calculator. Examples are illustrative, and published rules take precedence over simplified estimates.
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