How We Source Our Numbers
Policy last updated:
A landscaping calculator that is wrong costs real money: an under-ordered patio base, a lawn seeded at twice the rate it needed, a retaining wall specified without drainage. So it matters where the numbers come from. This page states the rule every tool on this site follows, and who is answerable for it.
Who builds these
These calculators are built and checked by Usama, a civil engineer. The subject matter overlaps directly with the discipline: retaining wall design, site drainage, grading and earthwork volumes, and aggregate material take-offs are all ordinary civil engineering work. That background is why the tools on this site treat a compaction allowance or a drainage gradient as a requirement rather than an afterthought.
It is also the limit of the claim. This is engineering judgement applied to published agronomic and horticultural data, not original agronomic research, and not a substitute for a licensed professional on a project where structural or drainage failure carries real consequences. Where a calculation approaches that line, the tool says so.
Where the numbers come from
Sources are used in the following order of preference. A figure from a lower tier is only used when nothing higher publishes one.
University extension services
State cooperative extension programmes: Penn State, Oregon State, Texas A&M AgriLife and their peers. Regionally specific, peer-reviewed, and written for practitioners rather than for marketing. This is the default first stop for seeding rates, soil amendment quantities and plant spacing.
Federal agencies
USDA and the Natural Resources Conservation Service for soil classification, plant hardiness and conservation practice standards. NOAA and the National Weather Service for frost dates, rainfall and evapotranspiration.
Published material specifications
Manufacturer technical data sheets and product labels for figures that are properties of a specific product: aggregate densities, block dimensions, emitter flow rates, coverage rates printed on the bag.
Industry standards bodies
ASTM, the Interlocking Concrete Pavement Institute, the Irrigation Association and equivalents, for installation tolerances and design conventions that no public agency publishes.
How a figure is accepted
Every published number traces to a source
If a figure appears in a calculator, a reference table or a worked example, it came from one of the tiers above. Sources are listed on the page itself, not buried in a site-wide disclaimer.
Formulas are confirmed against two independent sources
Before a calculator ships, its underlying formula is checked against at least two sources that do not cite each other. Where they disagree, the page says so and explains which convention it follows.
Ranges are reported as ranges
Real materials vary. Gravel density depends on the stone; seeding rates depend on the cultivar and the season. Where a source gives a range, the calculator carries the range through rather than collapsing it to a false single number.
Regional figures are labelled as regional
Frost dates, watering rates and cost estimates are not universal. Where a number only holds for a particular climate or market, the page states which.
What we do not do
- We do not copy figures from competing calculators. If another site is the only place a number appears, that is a reason to distrust it, not to repeat it.
- We do not generate numbers with a language model. AI assists with drafting prose; it is not a source of engineering data, and no figure enters a calculator on its authority.
- We do not invent precision. A number sourced as "roughly 2,800 lb per cubic yard" is not republished as 2,835.
- We do not treat marketing copy as a specification. A product page claim is used only when it also appears on the technical data sheet or the label.
Reviews and corrections
Every tool page carries a last updated date. That date reflects the last time the page's figures and sources were checked against their originals, not a cosmetic edit.
Going forward, each tool is reviewed at least annually, and sooner when a source publishes revised guidance or when a reader reports a problem. Seasonal tools (frost dates, seeding windows) are reviewed ahead of the season they apply to. This is the commitment the site is run on; pages record their own history through the dates they carry.
If you think a number here is wrong, please tell us. Emailcontact@bunnycorner.com with the tool and the figure in question, and a source if you have one. Corrections to a published number are made on the page, and the page's updated date moves with them.