Subfloor & Prep
The subfloor & prep cluster: an underlayment calculator (rolls = ceil(area ÷ roll coverage)), a self-leveling compound calculator (bags by depth × area), a subfloor sheet calculator (a 4×8 sheet = 32 sq ft), a floor-leveling / subfloor-prep cost tool, and a moisture / vapor-barrier coverage calculator. A subfloor sheet here is a coverage/prep quantity — joist span and floor load are for a qualified builder and local code.
Confirm coverage against your product’s box/spec sheet and buy 5–10% extra for cuts, waste and future repairs. Coverage and box sizes vary by brand.
Planning estimate: this is a planning estimate from the numbers you enter — not a bid or a contract. Flooring pricing depends on material, grade, subfloor condition, room complexity and local labor. Get itemized written quotes from licensed, insured flooring installers before you commit.
Underlayment CalculatorFind how many rolls of flooring underlayment to buy from your room area and the roll's coverage. Includes the formula, a worked example and FAQs.Self-Leveling Compound CalculatorEstimate how many bags of self-leveling compound you need from floor area, average pour depth and the bag's yield. Formula, worked example and FAQs.Subfloor Sheet CalculatorCalculate how many 4x8 plywood or OSB subfloor sheets cover your floor area. A coverage and prep quantity, not a structural design. With worked example.Floor Leveling & Subfloor Prep CostAdd up floor leveling and subfloor prep cost from area, your $/sq ft, materials and labor. A direct planning itemizer, not a bid. With a worked example.Moisture & Vapor-Barrier CoverageWork out how many rolls of moisture or vapor barrier cover your subfloor from the area and roll coverage. Includes the formula, an example and FAQs.
Every Subfloor & Prep tool is calculated server-side — visible immediately — with its formula, a worked example and a reference table, and works on the quantities you measure and the prices you enter from your own quotes. Background reading is in the guides.