Ice & Water Shield Calculator

About this calculator

Ice and water shield is a self-adhering, rubberized-asphalt roofing underlayment installed along eaves, valleys and other vulnerable areas before shingles go on. In cold climates it’s often required by building code — the IRC generally calls for it to extend from the eave’s edge to at least 24 inches inside the exterior wall line — because it seals around nail penetrations and stops water from ice dams backing up under shingles and leaking into the attic.

This calculator estimates how many rolls you need from your total eave length and the number of courses (rows) the shield must cover, accounting for standard roll coverage and overlap between courses. It’s used by roofing contractors and estimators quoting a job and by homeowners and DIYers planning a roofing project who need to know how much underlayment to buy before ordering materials.