Methodology & Sources
How numbers get on this site
Every empirical number lives in one data register. A register row is one of three things: a definition, which cannot be wrong or go stale; a sourced figure, which carries a source, a date and a verification level; or an assumption, which is labelled as ours and is editable. Nothing else is allowed in.
The build refuses to run if a material profile points at a missing register row, if a sourced row has no verification level, or if a row is past its next-due date. That is the technical enforcement of the accuracy rule, not a promise to be careful.
Verification levels
- secondary — the figure came through the named aggregation, and the primary supplier pages have not been opened. The date is when the aggregation was read. Every density row on this site is currently secondary.
- verified — the row's named primary page was opened, read and dated. None of the density rows is at this level yet.
- uncollected — no source has been collected for the row at all, so no value from it may be published. No row is in that state today. If one ever is, the build withholds every page that publishes a figure computed from it, and refuses to publish a hub or trust page that would.
Why the densities are secondary
Each density figure traces to one aggregation page that names its own supplier sources. Those primary supplier pages have not been opened individually, so the honest level is secondary and the page dates say so. Promoting a row to verified means opening the named primary page and recording a new date — not re-reading the same aggregation and calling the date a new verification.
The unit constants
The conversions (inch, foot, yard, pound, litre, cubic yard, cubic metre) are fixed by definition in the 1959 yard-and-pound agreement and published in NIST SP 811 Appendix B. They are exact, carry no verification date, and never appear in a data refresh.
Refresh cadence
Density and bag-yield rows are checked twice a year — spring before the mulch and soil season, autumn before sod season. Sod coverage is re-checked if a supplier changes its pallet. Unit constants are never refreshed, because they cannot change.
Attribution, not reproduction
Where a range came through a secondary aggregation, the aggregation is credited and its named primary suppliers are credited individually below. No table is copied wholesale from any source.
The register
This is the whole empirical surface of the site. If a number is not here, it is a formula or a user input.
| Key | Constant | Value used | Class | Source | Verification | Read / verified | Next due |
|---|---|---|---|---|---|---|---|
DEF | Unit conversions (inch, foot, yard, pound, short ton, litre, cubic foot, cubic yard, cubic metre) | see constants.mjs | definition | NIST SP 811, Guide for the Use of the International System of Units, Appendix B (2008 edition); international yard and pound agreement, 1959 | definition | n/a (exact, fixed by definition) | never |
GEO | pi = 3.14159265358979 | 3.14159265358979 | definition | mathematics | definition | n/a | never |
REG-03 | Shredded bark mulch density | 550 lb per cubic yard (range 500–600) | sourced | thewellkeptgarden.com aggregation (Mr. Mulch; Sands and Soils) | secondary - primary unverified | 2026-11-05 | 2027-03-01 |
REG-04 | #57 crushed stone and pea gravel density | 2700 lb per cubic yard (range 2,440–2,700) | sourced | thewellkeptgarden.com aggregation (South Bay Materials; Sands and Soils; Palmetto Sand & Gravel) | secondary - primary unverified | 2026-11-05 | 2027-03-01 |
REG-04b | Crusher run / road base density | 2475 lb per cubic yard (range 2,450–2,500) | sourced | thewellkeptgarden.com aggregation (Yard Works; Sands and Soils) | secondary - primary unverified | 2026-11-05 | 2027-03-01 |
REG-03b | Screened topsoil density | 2300 lb per cubic yard (range 2,200–2,600) | sourced | thewellkeptgarden.com aggregation (Sands and Soils; BlueStar Landscape Supply) | secondary - primary unverified | 2026-11-05 | 2027-03-01 |
REG-03c | Compost density | 1000 lb per cubic yard (range 800–1,500) | sourced | thewellkeptgarden.com aggregation (University of Minnesota Extension) | secondary - primary unverified | 2026-11-05 | 2027-03-01 |
REG-04c | Masonry / bedding sand density | 2800 lb per cubic yard (range 2,600–3,000) | sourced | thewellkeptgarden.com aggregation (Sands and Soils; Wild Toad) | secondary - primary unverified | 2026-11-05 | 2027-03-01 |
REG-05 | US/CA bagged volumes actually used by a tool: mulch 2 cu ft; topsoil 0.75 cu ft; aggregate 0.5 cu ft. Bag WEIGHT is a separate SKU attribute and is not interchangeable with a bag volume. | 2 (mulch) / 0.75 (soil) / 0.5 (aggregate) cubic feet per bag (range 0.5–2) | sourced | manufacturer pages (ScottsMiracle-Gro, SAKRETE, QUIKRETE) + retailer catalogues (Street Stores; Baeten's), read 2026-11-05 | secondary - manufacturer body text for 0.75 cu ft and 50 lb; retailer/catalogue for 2 cu ft; aggregate volume derived from SAKRETE yield statement; Home Depot/Lowe's/Ace/Rona/McCoy's/Blain's/Tractor Supply blocked the fetcher | 2026-11-05 | 2027-03-01 |
REG-05m | Metric bag volumes: 50 L (GB); 25 L (AU). Each is the product's own label, not a conversion of a US bag (AU 25 L is not the US 0.5 cu ft bag, 14.16 L). | 50 L GB / 25 L AU litres per bag (range 25–50) | sourced | product names on manufacturer/merchant pages (UK: Natural Grower, Darlaston; AU: Brunnings, ID Garden Centre), read 2026-11-05 | secondary - title-depth only: the bag size appears in the product name/h1, not in readable body text, so no coverage statement was verified | 2026-11-05 | 2027-03-01 |
REG-06 | Sod coverage: roll 10 sq ft; pallet 500 sq ft (observed range 450-600); slab 16 x 24 in = 2.667 sq ft | 10 / 500 / 2.667 sq ft per unit (range 10–600) | sourced | MSU Extension P2951 + three sod farms (Aldino, Genesis, Coosa Valley), read 2026-11-05 | verified - primary pages opened and read: extension publication and sod-farm product data, body text. Slab 2.667 is SINGLE-SOURCE (Coosa Valley only). Pallet 500 is a chosen default inside a sourced 450-600 range, not a sourced constant. | 2026-11-05 | 2027-03-01 |
REG-07 | Overage defaults: sod 5%; mulch and soil 10%; aggregate 5% | 5 / 10 / 5 percent | assumption | our editable default (not a published standard) | assumption - our default, editable | n/a | review at Gate D |
REG-08 | Bulk rounding increments per region: 0.5 cu yd (US/CA); 0.5 m3 (metric). Two independent sold increments, not conversions of one another (0.5 m3 = 0.654 cu yd). | 0.5 cu yd / 0.5 m3 per step | assumption | supplier practice (assumption) | assumption - supplier practice, editable | n/a | review at Gate D |
REG-09 | Example prices | per tool currency per unit | example | example value, check your supplier | example - not a published price | n/a | never (user-entered) |
Unit constants
| Conversion | Value | Basis |
|---|---|---|
| inch → mm | 25.4 exactly | international yard and pound agreement 1959; NIST SP 811 App. B |
| foot → m | 0.3048 exactly | same |
| yard → m | 0.9144 exactly | same |
| lb → kg | 0.45359237 exactly | same |
| 1 US short ton | 2,000 lb | US customary, by definition |
| 1 tonne | 1,000 kg | SI |
| 1 cu ft | 28.316846592 L | derived, exact |
| 1 cu yd | 764.554857984 L = 27 cu ft | derived, exact |
| 1 m³ | 35.31466672 cu ft | derived, exact |
| π | 3.14159265358979 | mathematics |
Attribution
Density ranges came through one named aggregation, The Well-Kept Garden, which credits its own supplier sources: Mr. Mulch and Sands and Soils (mulch); South Bay Materials, Sands and Soils and Palmetto Sand & Gravel (aggregate); Sands and Soils and BlueStar Landscape Supply (topsoil); University of Minnesota Extension (compost); Sands and Soils and Wild Toad (sand). Those primary pages have not been opened individually, which is why every density row is marked secondary.
Where each register row stands
Every register row has a source, a date and a level, and no row is uncollected. The bag-volume and sod rows were collected on 2026-11-05 and each says what it rests on: REG-05 is secondary because two of its three figures come from retailer catalogues and the aggregate volume is arithmetic on a manufacturer's yield statement; REG-05m is secondary and title-depth only, because the bag size appears in the product name rather than in body text; REG-06 is verified from primary pages, with its slab figure marked single-source and its pallet figure marked a chosen default inside a sourced 450-600 sq ft range. If a row's source is ever withdrawn, the build reverts that row to uncollected and withholds any page that publishes a figure computed from it.
Found a number that looks wrong? Tell us on the contact page — we cite the source for every constant and correct errors in public with the date.