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Flooring & TileFloor Underlayment Calculator — How Many Rolls Do I Need?
Estimate rolls of underlayment for a laminate or engineered floor, based on about 100 sq ft per roll. Roll sizes vary, so confirm the coverage printed on yours.
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How this calculator works
We take the room area, add 5% for overlap and trimming, and divide by about 100 sq ft per roll — a common foam-underlayment size. Cork, felt, and premium rolls differ, so check your product.
What changes how much you need
- Roll coverage varies a lot — standard foam is ~100 sq ft, but others differ; check the label.
- Many click-lock floors come with attached padding and need no separate underlayment.
- Overlap or butt seams exactly as the instructions say, and tape them.
- Over concrete, use an underlayment with a built-in moisture barrier (or add one).
Frequently asked questions
How many square feet are in a roll of underlayment?
Often about 100 sq ft for standard foam, but premium, cork, and felt rolls vary — read the packaging.
Do I need underlayment under laminate?
Usually yes, unless the planks already have attached padding. It cushions, quiets, and evens out minor subfloor imperfections.
Do I need a moisture barrier?
Over concrete or below grade, yes. Use underlayment with a built-in vapor barrier or lay one first.