Methodology
The calculator works in metres, square metres, cubic metres and kilograms at full floating-point precision. Units are converted only for input and display.
Geometry
Rectangle: A = length × width. Circle: A = π × (diameter ÷ 2)². Triangle: A = base × height ÷ 2. Volume for each area is A × depth.
The base volumes of all valid areas are summed. An extra percentage z is then applied as V × (1 + z/100). Adding 10% means multiplying by 1.10, not dividing by 0.90.
Exact conversions
| Unit | SI value |
|---|---|
| 1 inch | 0.0254 m |
| 1 foot | 0.3048 m |
| 1 ft² | 0.09290304 m² |
| 1 ft³ | 0.028316846592 m³ |
| 1 yd³ | 0.764554857984 m³ = 27 ft³ |
| 1 US short ton | 907.18474 kg |
Typical depths by project
These are editable planning presets, not site-specific recommendations and not automatic instructions to import that entire depth of topsoil. Soil tests, existing grade, drainage and plant needs may require a different depth.
| Preset | Value | Source |
|---|---|---|
| Lawn 6 in | 6 in | Illinois Extension — Preparing Lawn Soil and Site Illinois Extension describes a goal of at least six inches of well-prepared soil. This is a planning reference, not a universal instruction to import six inches of topsoil. |
| Bed 12 in | 12 in | University of Maryland Extension — Soil to Fill Raised Beds Maryland Extension gives 8 inches as a minimum for some crops on hard surfaces and 12–24 inches for peppers, tomatoes and squash. Use the actual fill depth. |
| Top-dress ½ in | 0.5 in | Clemson Cooperative Extension — Topdressing A Home Lawn Clemson says applications should be light and no more than ½ inch at a time; routine top-dressing may be thinner. |
Typical density
| Material | Planning value | Source |
|---|---|---|
| Topsoil — typical range | 1100–1600 kg/m³; midpoint 1300 | USDA NRCS — Soil Bulk Density / Moisture / Aeration Planning range only; moisture and compaction change weight. Prefer supplier data. |
Bags, bulk orders and money
Full bags are rounded up only after all areas are summed. Bulk quantity is raised to the supplier minimum and then rounded up to the chosen increment. A blank price is not treated as zero. Costs are evaluated with decimal arithmetic and shown to two decimal places.
Limits
This tool estimates material quantity. It does not assess soil quality, structural loading, drainage, compaction, truck access or local supplier rules.