Methodology

This page explains how the LandscapingCalcs calculators are derived and verified — and why they need no ongoing maintenance to stay correct.

1. Timeless math, stable conventions

Every tool computes from a closed-form formula: bulk volume cu yd = area × depth ÷ 324; tons = cu yd × density; grass seed lb = area × rate ÷ 1,000; sod pallets = area ×(1+waste) ÷ 450; fertilizer lb = (N rate ÷ 1,000 × area ÷ 1,000) ÷ (%N ÷ 100); pavers = ceil(area ×(1+waste) ÷ paver face); retaining-wall blocks = wall face ÷ block face; fence posts = ceil(length ÷ spacing) + 1; deck boards = area ÷ board coverage ×(1+waste); post concrete = hole volume ÷ bag yield; watering gal = area × inches × 0.623; plant count = area ÷ spacing²; project cost = quantity × your unit price. The only baked-in numbers are stable conventions — 324, 27 cu ft per cu yd, 0.623 gal per sq ft per inch, ~13.5 bags per cu yd, ~450 sq ft per pallet — plus labeled coverage, density, seeding and spacing typicals. These do not drift, so the statements stay true over time.

2. No prices, no feeds

There is deliberately no material or service price, no labor-rate table, no regional cost index and no product catalog. Every cost tool works on the prices you enter from your own quotes and bills ($/cu yd, $/sq ft, $/ft, $/tree, $/acre, $/hour). That is why the site is correct regardless of what materials, labor or service prices do.

3. Numeric self-check

Every formula is asserted against a worked example with known numbers (for instance: 300 sq ft of beds at 3 in deep is 2.78 cu yd, about 38 bags of 2 cu ft; a 2,000 sq ft lawn takes 5 pallets of sod; a 200 sq ft patio in 4×8 pavers needs about 946 pavers; a 100 ft fence at 8 ft spacing needs 14 posts and about 209 pickets; 200 sq ft of gravel at 4 in is 2.47 cu yd, about 3.46 tons). A release gate runs all of these and fails on any mismatch, so "verification" here is mathematical correctness plus accurate conventions — not a time-based check.

4. Estimate, not a bid, design or prescription

The coverage, density, seeding, paver and spacing values are labeled planning typicals — a starting point, not a spec. Every material result is a planning estimate: coverage varies by product, so buy about 5–10% extra and confirm on the bag. Every cost result is a planning estimate: get itemized written quotes from licensed, insured landscapers and contractors. Tree removal and land clearing are dangerous — hire a licensed, insured arborist. Retaining walls over about 3–4 ft usually need an engineer and a permit; confirm with your local building department. Nothing here is landscape-engineering design or a horticultural prescription.