Methodology

This page explains how the FloorsCalcs 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: material needed = area × (1 + waste); boxes = ceil(material ÷ box coverage); tiles = ceil(area × (1 + waste) ÷ tile size); carpet sq yd = area ÷ 9 × (1 + waste); rolls = ceil(area ÷ roll coverage); leveler bags = ceil(area × depth ÷ bag yield); subfloor sheets = ceil(area ÷ 32); trim pieces = ceil(linear ft ÷ piece length); grout lb = area × labeled lb/sq ft; thinset bags = ceil(area ÷ sq ft per bag); install cost = (area × your $/sq ft + labor + Σ add-ons − discount) ×(1 + contingency). The only baked-in numbers are stable identities (9 sq ft = 1 sq yd, a 4×8 sheet = 32 sq ft, ceil for whole units, room geometry) and labeled industry planning typicals (waste % by pattern, box/tile coverage, grout/thinset coverage, expansion gap & acclimation). These do not drift, so the statements stay true over time.

2. No prices, no feeds

There is deliberately no material or labor price, no regional cost index, no product catalog, no installer directory and no live rate. Every cost tool works on the prices you enter from your own quotes and bills ($/sq ft for material, $/hr or flat labor, $/bag, $/roll, $/ft). Labeled cost bands are shown only as a sanity guide. That is why the site is correct regardless of what material or labor prices do.

3. The grout-coverage derivation

The grout calculator uses a labeled coverage in lb per sq ft looked up by tile size and joint width. The underlying physics is grout_lb/sq ft ≈ ((L + W) ÷ (L × W)) × joint_width × joint_depth × density — smaller tiles (more joint per sq ft) and wider joints use more grout. We publish the labeled coverage and let you confirm it against your grout bag, which already prints a coverage chart.

4. Numeric self-check

Every formula is asserted against a worked example with known numbers (for instance: a 200 sq ft room at 10% waste needs 220 sq ft — 11 boxes at 20 sq ft a box; a flooring install of 200 sq ft at $5/sq ft + $400 labor + $500 add-ons at 10% contingency is about $2,090; a 100 sq ft tile floor at $10/sq ft + $500 labor is $1,650; 100 sq ft of 12×12 tile with a 1/4" joint takes about 10 lb of grout; 120 sq ft leveled 1/2" deep takes 6 bags; refinishing 400 sq ft at $3/sq ft + $200 stain is about $1,540). 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.

5. Estimate or quantity guide, not a bid or a spec

The contingency %, waste %, box/tile coverage, grout/thinset coverage, expansion gap and cost bands are labeled planning typicals — a starting point, not a spec. Every result is a planning estimate or a material-quantity guide: get itemized written quotes from licensed, insured flooring installers, confirm coverage on your product’s box/spec sheet, and buy 5–10% extra for cuts, waste and future repairs. A subfloor sheet is a coverage/prep quantity, not a structural design; a heated-floor mat is a user-entered cost line-item, not a heat-load calculation. Nothing here is an installation procedure, an engineering determination, or safety advice.