Underlayment Calculator

Estimate how much underlayment to order for a flooring job. Accounts for seam overlap and a waste factor for cuts.

Underlayment Needed
— sq ft
Includes overlap and waste.

Usage Tip

Check the flooring spec first; some products have underlayment attached and need none, while others require a specific type.

THE MATH
overlap factor = 1 + (overlap ÷ 12 ÷ 4)
order = area × overlap factor × (1 + waste ÷ 100)
Underlayment is the cushioning or moisture layer rolled out under laminate, vinyl, or engineered wood.
Rolls overlap at the seams, so you order more than the bare floor area.
Enter the floor area, the seam overlap in inches, and a waste percentage for cuts.
The overlap factor assumes seams roughly every 4 feet.
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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.