Methodology

Deterministic, versioned arithmetic. No AI for numbers. Money in whole minor units (USD cents), metric, and a strict split between markup — % on cost — and margin — % on price.

Common rules

• buy_qty = net × (1 + waste), with adjustable waste.
• Purchase rounded UP to sellable units (boxes, bags, buckets, boards).
• Invalid inputs (negatives, zero where not allowed, NaN, Infinity, mixed units) are rejected with a clear error.
• Configurable tax per country profile (USA default 0% — no federal sales tax; set your state rate).

Formulas per calculator (v1.0.0 · verified 2026-09-10)

• Wall & ceiling area calculator — see formula on its pagenet = Σ(length × height) + ceiling − openings; buy = net × (1 + waste)
• Paint calculator — see formula on its pagenet_litres = area ÷ coverage × coats; buy = net × (1 + waste); buckets = ceil(buy ÷ bucket)
• Tile calculator — see formula on its pagenet_pcs = area ÷ (width × length); boxes = ceil(area × (1+waste) ÷ m² per box)
• Adhesive & grout calculator — see formula on its pagekg = area × consumption; bags = ceil(kg × (1+waste) ÷ bag)
• Drywall calculator (boards) — see formula on its pagenet_boards = area × sides ÷ (width × length); buy = ceil(net × (1+waste))
• Framing & screws calculator — see formula on its pagetracks = ceil(2L ÷ 3); studs = floor(L ÷ spacing) + 1; screws ≈ 25 × m²
• Brick calculator — see formula on its pagepcs = area × pcs/m²; buy = pcs × (1+waste)
• Concrete block calculator — see formula on its pagepcs = area × 12.5; buy = pcs × (1+waste)
• Mortar calculator — see formula on its pagekg = m² × kg/m²; bags = ceil(kg × (1+waste) ÷ bag)
• Concrete calculator — see formula on its pageslab V=l×w×t; footing V=l×w×d; column V=πr²h; wall V=l×h×t; stairs V=n×(tread×riser/2)×w; ramp V=(l×h/2)×w; round V=πr²×t; ring V=π(R²−r²)×h; order = V×(1+waste)
• Cement, sand & gravel calculator — see formula on its pagecement = V × kg/m³; aggregates = V × m³/m³; all × (1+waste)
• Laminate flooring calculator — see formula on its pagebuy_m² = area × (1+waste); boxes = ceil(buy_m² ÷ m²/box)
• Baseboard calculator — see formula on its pagenet = perimeter − doors; pieces = ceil(net × (1+waste) ÷ piece)
• Labor & margin calculator — see formula on its pagemarkup_sale = cost × (1+m); margin_sale = cost ÷ (1−m)
• Full renovation estimator — see formula on its pagetotal = Σ(area × $/m² per chapter)

Limits

• Quantity estimation, not structural design or site supervision.
• Where professional judgment is required (structure, MEP), the page says so.
• Prices and coverage are indicative unless you use your saved prices.