Siding Calculator

Calculate siding squares, trim, fasteners, and material cost for vinyl, fiber cement, wood, or metal siding.

Wall Input Mode

Wall Length (ft)

Used for all 4 walls

Wall Height (ft)

Siding Type

Doors (qty)

Windows (qty)

Waste %

Deductions: 21 sqft per door, 15 sqft per window (industry standard). Trim includes J-channel, starter strip, and corner posts.

Total Material Cost

$7,091

1,406 sqft Vinyl · 306 LF trim

Gross Wall Area	1,440 sqft
Deductions (2 doors + 8 windows)	−162 sqft
Net Wall Area	1,278 sqft
Siding Needed (+10% waste)	1,406 sqft
Squares (100 sqft each)	14.1 squares
Siding Cost (1,406 sqft @ $4.50)	$6,326
Trim (306 LF @ $2.50/LF)	$765
Fasteners / Nails (est.)	1,055 pcs
Total Material Cost	$7,091

construction

Contractor Note — Mike Callahan

Fiber cement lasts 50 years but it's heavy — you need two guys to carry a 12-foot plank. Budget for 20% more labor vs vinyl. And always back-prime the cut ends or it'll wick moisture and fail in 10 years instead of 50.

Methodology

Gross wall area = sum of all wall lengths x heights. Deductions: 21 sqft per exterior door (3ft x 7ft), 15 sqft per standard window (3ft x 5ft). Siding needed = net area x (1 + waste%). Vinyl is sold by the "square" (100 sqft). Trim estimate: house perimeter + 17 LF per door (2 sides + header) + 14 LF per window (4 sides), at $2.50/LF covering J-channel, corner posts, and starter strip. Fastener count at 0.75 nails per sqft of siding.

Frequently Asked Questions

How many squares of siding do I need for a house?

A "square" of siding covers 100 sqft. For a typical 1,500 sqft ranch-style home (about 40ft x 30ft with 9ft walls), the gross wall area is roughly 1,260 sqft. After deducting for doors and windows (typically 150-200 sqft), you need about 1,060-1,110 sqft of net siding. Add 10% waste and you need 12-13 squares. Two-story homes double the wall height but keep the same perimeter, so plan for 22-26 squares for a 2,500 sqft colonial.

Vinyl vs fiber cement siding: which lasts longer?

Fiber cement (like James Hardie) lasts 40-50 years with proper maintenance and holds paint for 15-20 years between repaints. Vinyl lasts 20-30 years but can crack in extreme cold, warp in extreme heat, and fades over time with no option to repaint. Fiber cement is also Class 1A fire-rated and resists termites and rot. The tradeoff: fiber cement costs nearly double in materials and labor, weighs 2.5 lbs/sqft vs 0.5 lbs/sqft for vinyl, and requires painting every 15 years.

What about starter strip and J-channel?

Starter strip runs along the bottom of the first course — you need one piece per linear foot of wall base (the house perimeter). J-channel goes around every door, window, and where siding meets soffit — plan for 17 LF per door and 14 LF per window, plus the full perimeter where walls meet the soffit. Outside corner posts (2 per corner, 1 wall height each) and inside corner posts are also needed. This calculator includes these in the trim cost estimate at $2.50/LF.

How much trim do I need for siding?

As a rule of thumb, trim linear footage equals the house perimeter (for starter strip and soffit trim) plus 17 LF per door plus 14 LF per window. For a 140-foot perimeter house with 3 doors and 10 windows: 140 + 51 + 140 = 331 LF of trim. Add 10% for waste and cuts. Corner posts, utility trim, and specialty pieces are extra — budget an additional 15-20% beyond the base trim estimate for a complete job.