Methodology
How our calculators work and where the numbers come from.
Quantity calculation
Volumes computed in cubic feet, converted to cubic yards by dividing by 27. Counts always rounded up — you cannot buy a partial unit.
Waste factor
Configurable waste factor (typically 5–15%) applied for compaction, off-cuts, and breakage. Every page shows the exact formula and inputs used.
Cost estimate
Quantity multiplied by national-average unit price, then by a regional multiplier. Every price is editable — drop in a local quote and recalculate.
Key constants
| Material / Constant | Value |
|---|---|
| Crushed stone density | ≈ 1.35 tons / yd³ |
| Pea gravel density | ≈ 1.40 tons / yd³ |
| Sand density | ≈ 1.45 tons / yd³ |
| River rock density | ≈ 1.30 tons / yd³ |
| 80 lb concrete bag yield | ≈ 0.60 ft³ |
| 60 lb concrete bag yield | ≈ 0.45 ft³ |
| 40 lb concrete bag yield | ≈ 0.30 ft³ |
| Drywall sheet (4×8) | 32 ft² |
| Drywall sheet (4×12) | 48 ft² |
| Paint coverage | ≈ 350 ft² / gallon / coat |
| Mulch formula | Area (ft²) × depth (in) ÷ 324 |
These are industry-standard values; real-world figures vary with moisture, compaction, product, and technique. Treat outputs as close estimates.
How cost is estimated
Each quantity is multiplied by a national-average unit price, then by a regional multiplier. Prices cover material only — they exclude delivery, equipment rental, and labor. Every unit price is editable.
Price data sources
Our baseline unit prices (last updated 2026-06-20) are national averages compiled and cross-checked from major home-center listings (Home Depot, Lowe's, Menards) and published cost-guide aggregators (HomeGuide, Fixr, HomeAdvisor/Angi, Concrete Network).
We use material-only prices (excluding delivery and labor), drop outliers, and take a defensible mid-range figure. Prices move with the market — edit any unit price in a calculator to match a local quote, and always confirm before purchasing.
See the full disclaimer. Estimates are not professional quotes.