Underlayment Roll Count Calculator

Measure the floor as a rectangle or type a known square footage, then add an overlap percentage for seams, door cutouts, and wall returns. Divide that by the coverage printed on the roll and round up, since rolls are sold whole. Some click-together LVP has an attached pad and may not need a separate underlayment at all, so check the flooring instructions before you order. In metric mode you enter meters and square meters and see both systems; the roll-coverage list shows the same roll sizes labeled either way.

How do you plan underlayment with overlap?

Measure the rectangle or type a known area, then enter the coverage from the roll label. Choose an overlap percentage (the tool starts at 5 percent). The square footage to order is the floor area increased by that percentage, and the number of rolls is that figure divided by the coverage on one roll, rounded up to the next whole roll.

Why does underlayment need an overlap percent?

Rolls rarely land on exact room dimensions. Seams, door cutouts, and wall returns use up a little coverage beyond the flat rectangle. A 5 percent overlap is a light allowance; 10 percent is safer when the room has many closets or the manufacturer wants generous side laps. This percentage is not a moisture-control factor – vapor-retarder rules come from the flooring system instructions.

Foam vs cork vs felt – does the math change?

The math is the same for foam, cork, felt, and thin polyethylene sheet: the square footage to order divided by the coverage on one roll, rounded up. What changes is the acoustic rating, the thickness, and whether the finished floor allows the product. Always match the underlayment to the flooring warranty requirements.