Underlayment Calculator

Calculate how many rolls or square feet of underlayment you need for your flooring project.

Use decimals when needed. This estimate updates live and is safe to tweak before you buy materials.

Estimated underlayment

Underlayment Buying Guide

This guide helps you turn your underlayment calculator result into a cleaner purchase plan. Use it when you want fewer return trips, better waste assumptions, and a more realistic cart.

Step 1: Read the flooring warranty

Many modern laminate and vinyl planks come with underlayment pre-attached to the bottom. Adding a second soft layer of underlayment will void the warranty and cause the joints to snap.

Step 2: Prioritize moisture barriers on concrete

If you are installing over a concrete slab or in a basement, you absolutely must buy an underlayment with a built-in 6-mil vapor barrier to block rising moisture.

Step 3: Buy the specialized tape

The rolls of underlayment must be taped together at the seams to create a continuous barrier. Buy the manufacturer's recommended foil or moisture tape.

Underlayment cost planning rule of thumb

Premium cork or heavy rubber underlayment costs significantly more than basic foam, but it drastically reduces the hollow 'clicking' sound of floating floors.