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Methodology, formulas & sources
Updated May 2026 3 min read
Every calculator on this site shares one math library. This page is the source of truth for the formulas and density assumptions. Real product weight varies by moisture, compaction, and supplier — we always show the assumption with each result.
Volume formulas
| Quantity | Formula |
|---|---|
| Cubic feet | area (sq ft) × depth (in) ÷ 12 |
| Cubic yards | cubic feet ÷ 27 |
| Cubic meters | cubic feet × 0.0283168 |
| Tons | cubic feet × density (lb/ft³) ÷ 2000 |
| Bag count | cubic feet ÷ bag size (cu ft), rounded up |
| With settling | baseline cubic feet × (1 + buffer) |
Density library
Values shown are landscape-industry typicals. The range column is the realistic spread we observe across suppliers.
Sources
- USDA NRCS soil bulk density references — for topsoil weight ranges.
- ASTM D-7382 / industry references — for aggregate (gravel, sand, paver base) bulk densities.
- Lowe's, Home Depot, Kurtz Bros & Mulch.com published bag-yield averages — for bag-size mapping.
- ACI 211.1 / Quikrete published yields — for concrete bag yield (60 lb → 0.45 cu ft, 80 lb → 0.60 cu ft).