Soffit & Fascia Calculator

Soffits are the horizontal panels that cover the underside of roof overhangs, stairways, and ceiling drops. Calculating soffit area and material needs correctly before buying prevents both wasteful over-ordering and frustrating mid-job shortages.

Formula: Soffit Area = Total Linear Feet of Overhang × Overhang Depth

Sheets or panels needed: Sheets = (Total Area × Waste Factor) ÷ Panel Area

That covers a flat soffit, which is what most eaves use. A boxed soffit wraps a return down the side of the overhang as well, so add twice the side height times the run to the area before dividing.

What each variable means:

• Overhang Depth: measured from the wall face to the fascia board. Typical residential overhang: 12–24 inches.
• Linear Feet: the total perimeter length where soffits are installed.
• Panel Area: standard vinyl soffit panels are typically 12 inches wide × 12 feet long = 12 sq ft per piece. Aluminum and wood panels vary.
• Waste Factor: use 1.10 for straight runs; 1.15–1.20 for corners and angles.

Worked example: A house has 120 linear feet of eave overhang, 18 inches (1.5 ft) deep.

Soffit area = 120 × 1.5 = 180 sq ft With 10% waste: 180 × 1.10 = 198 sq ft Standard vinyl panels (12 sq ft each): 198 ÷ 12 = 17 panels (round up to 17)

Material types:

• Vinyl: low maintenance, fine in most climates, the cheapest of the four
• Aluminum: durable, paintable, fire-resistant, a step up in price
• Wood (cedar, pine): traditional look, needs painting or staining, dearer again
• Fiber cement: most durable, rot and fire resistant, usually the priciest

Material prices move enough by region and year that any figure printed here would be stale before you read it. Get a per-square-foot quote from your supplier and multiply it by the area above.

Always order 10–15% extra to account for future repairs. Matching panels years later can be difficult once a profile is discontinued.