Roof Underlayment Calculator

Enter your roof area to find out how many rolls of underlayment you need. Compare 15 lb felt, 30 lb felt, and synthetic options to find the most cost-effective choice for your project.

Roof Area (sq ft)

Overlap (in)

Waste Factor (%)

Pricing (edit to match local rates)

15 lb Felt Roll ($)

30 lb Felt Roll ($)

Synthetic Roll ($)

Cap Nails Box ($)

Staples Box ($)

Roof Area (with waste)

2,200 sq ft

2,000 sq ft + 10% waste

Rolls Needed

12 rolls

192 sq ft effective per roll

Recommended Buy

15 lb Felt

6 rolls · $225.00

Purchase Option	Quantity	Est. Cost
15 lb FeltBest value	6 rolls	$225.00
30 lb Felt	12 rolls	$495.00
Synthetic	3 rolls	$255.00

Cheapest option: 15 lb Felt at $225.00Synthetic underlayment costs more per roll but covers significantly more area, making it cheaper for large roofs. For smaller roofs or budget jobs, 15 lb or 30 lb felt is often more economical. Synthetic is also more durable and can be left exposed longer before shingle installation.

This is a material estimate only. Actual coverage varies by roof complexity, valleys, and penetrations. Always order extra to account for cuts and waste around dormers, vents, and skylights.