Floor Underlayment Calculator

Measured area (sq ft). Enter the floor surface receiving this underlayment. Measure the installation area before adding cutting waste. Separate products or layers that have different coverage or installation requirements.

Effective coverage per roll/package (sq ft). Use the effective installed coverage of one roll or package after the required seam overlaps. The raw roll dimensions may cover more area than the finished installation. Do not count those same overlaps again in the waste allowance.

Allowance (%). Enter the percentage you want to add for cutting, handling loss or other conditions specific to this work. Apply it to the measured quantity rather than enlarging the measurements as well. The suggested value is editable, not a universal recommendation; enter zero when no allowance is needed.

Required coverage includes the cutting allowance. Packages round that coverage demand upward, and purchased coverage is the effective installed area of those complete packages. Tape, perimeter upturns, transitions and other accessories are not added automatically.

Required area = floor area × (1 + cutting waste ÷ 100). Packages = ceil(required area ÷ effective package coverage). Purchased coverage = packages × effective coverage.

Worked example: 400 sq ft with 10% cutting allowance requires 440 sq ft. At 90 effective sq ft per roll after overlaps, buy 5 rolls (450 effective sq ft).

Use effective coverage for the selected product and seam system. This is not a moisture, acoustic, fire-rating, or flooring-compatibility assessment. Tape, transitions and perimeter upturns need separate allowances.