Source ledger
We reviewed these primary references for the current planning guidance on 1 October 2026. The formulas for geometry and unit conversion are arithmetic; installation advice and rates require local and product guidance.
- University of Maryland Extension: Determining the area/size of a practice
- University of Minnesota Extension: Soil testing for lawns and gardens
- Penn State Extension: Lawn establishment
- Penn State Extension: Turfgrass seed and seed mixtures
- University of Minnesota Extension: Mulching for soil and garden health
- Concrete Masonry & Hardscapes Association: Paver technical guidance
- US EPA WaterSense: Water Budget Tool
- University of Maryland Extension: Rain garden fact sheet
Calculators identify editable assumptions. A source may describe a particular region or system; it is not a universal material specification.