Flooring Underlayment Calculator
Calculates roll requirements for floating floor foam underlayment, acoustic cork sheets, concrete slab 6-mil polyethylene vapor barrier film, and tile uncoupling membranes.
Formula
Total Area = Length × Width × (1 + Overlap %); Rolls = Ceil(Total Area ÷ Roll Coverage)
1. Net Area = Length × Width 2. Gross Area = Net Area × (1 + Overlap %) 3. Rolls to Order = Ceil(Gross Area ÷ Roll Coverage)
Inputs
- Room Length
- Room Width
- Underlayment Material
Worked example
Laying 3-in-1 acoustic foam underlayment (100 sq ft rolls) over concrete before vinyl plank.
Outcome: Net area is 300 sq ft. With 8% overlap allowance (324 sq ft total), you need 3.24 rolls, rounding up to 4 full 100 sq ft rolls.
Do I need 6-mil poly vapor barrier over a wood subfloor?
No! Never put a plastic vapor barrier over a wood subfloor on upper floors, as it can trap ambient moisture and cause the wood subfloor to rot. Plastic vapor barriers are strictly for concrete slabs.