Soffit & Fascia Calculator
Calculate soffit area, fascia board footage, and J-channel from perimeter and eave width.
Returns quantities for aluminum, vinyl, and wood soffit.
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
For box soffits (three panels — bottom and two sides): Total Material = Bottom Area + (2 × Side Height × Length)
Sheets or panels needed: Sheets = (Total Area × Waste Factor) ÷ Panel Area
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 and typical costs:
- Vinyl: $1.00–$3.00/sq ft — low maintenance, good for most climates
- Aluminum: $2.00–$5.00/sq ft — durable, paintable, fire-resistant
- Wood (cedar, pine): $3.00–$8.00/sq ft — traditional look, requires painting/staining
- Fiber cement: $4.00–$7.00/sq ft — most durable, rot and fire resistant
Always order 10–15% extra to account for future repairs — matching panels years later can be difficult.