How to measure a house for siding
Siding is ordered in squares. One square covers 100 sq ft of wall. To find yours, measure the walls, add the gables, take off the openings and add a waste factor. Here is the math with the calculator's starting house: 40 x 30 ft, two stories, two gables at a 6/12 pitch, 12 windows, 2 doors and vinyl siding.
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1
Walls: perimeter times height
(40 + 30) × 2 = 140 ft around. At 18 ft from the foundation to the eaves, that is 2,520 sq ft.
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2
Gables: half of width times rise
A 6/12 roof rises 6 inches per foot, so over half of a 30 ft width it rises 7.5 ft. Each gable is ½ × 30 × 7.5 = 112.5 sq ft. Two gables add 225 sq ft.
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3
Subtract the openings
About 15 sq ft per window, 21 sq ft per entry door and 112 sq ft per two-car garage door. 2,745 − 180 − 42 = 2,523 sq ft of siding.
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4
Add waste and convert
2,523 × 1.10 = 2,775 sq ft, or 27.8 squares. A double 4-inch vinyl panel 12 ft 6 in long covers 8.33 sq ft, so that is 334 panels.
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5
Add the trim
J-channel goes around every window and door and along the eaves and gable rakes: about 373 ft here, or 33 pieces with 10% extra. Each of the 4 corners needs two 10 ft posts on an 18 ft wall, and starter strip runs the 140 ft perimeter.
With house wrap, tape and nails, the materials for this house come to about $4,346 at the default prices. That is what the calculator shows when it opens.
Siding pieces and coverage
What one piece covers depends on its length and its exposure, the part left showing after the next course overlaps it.
| Siding | Typical piece | Covers | Per square |
|---|---|---|---|
| Vinyl | Double 4 in, 12 ft 6 in | 8.33 sq ft | 12 panels |
| Fiber cement lap | 8¼ in, 12 ft, 7 in exposure | 7 sq ft | about 14.3 |
| Engineered wood lap | 8 in, 16 ft, about 6.9 in exposure | 9.25 sq ft | about 10.8 |
| Cedar bevel | 8 in, 14 ft, 6¼ in exposure | 7.3 sq ft | about 13.7 |
| Steel lap | Double 4 in, 12 ft | 8 sq ft | 12.5 |
Vinyl usually ships in boxes of 2 squares. Fiber cement and engineered wood are sold by the piece. Lengths and exposures vary by brand, so check the product sheet and type your own price per square foot into the calculator.
Siding materials compared
| Material | Material per sq ft | Installed per sq ft | Upkeep and life |
|---|---|---|---|
| Vinyl | $1.00–$1.50 | $3–$12 | No paint. Can crack on impact and warp near heat. Lifetime limited warranty for the first owner is common. |
| Fiber cement | $2.15–$3.85 | $5–$14 | 50+ years. Repaint every 10–15 years. Heavy; cutting makes silica dust. |
| Engineered wood (LP) | $1.85–$2.20 | $2–$10 | Lighter, cuts like wood. 5/50-year limited warranty. Keep paint and edges sealed. |
| Cedar | $5–$6 | $2–$15 | Real wood look. Needs regular stain or paint; rot, insects and woodpeckers are risks. |
| Steel | about $4–$5 | $4–$16 | Will not rot or burn. Can dent, and scratches need touch-up to stop rust. |
The installed ranges are wide because they cover everything from a one-story ranch with long, plain walls to a three-story house with dormers. In the 2025 Cost vs. Value report, an average vinyl replacement on 1,250 sq ft of wall cost about $18,000 and recouped about 97% at resale. Fiber cement cost about $21,500 and recouped about 114%. Those jobs include tearing off the old siding and new trim.
Trim and accessories
- Starter strip runs along the bottom of every wall and locks in the first course.
- J-channel (vinyl and steel) frames windows and doors and catches the cut ends under eaves and along gable rakes. With fiber cement and wood siding, 1x4 trim boards do this job instead.
- Corners: vinyl uses one-piece corner posts, usually 10 ft long. Fiber cement and wood use two trim boards per corner. Inside corners need their own posts or a square trim board.
- Soffit and fascia: soffit closes the underside of the roof overhang and should be vented where your attic needs air. Fascia covers the board at the rafter tails. They are optional here because many houses keep the old ones.
- House wrap: the International Residential Code (section R703.2) requires a water-resistive barrier behind siding. Lap it like shingles, top over bottom, and tape the seams.
Tips from the pros
- Hang vinyl loose. Vinyl grows and shrinks with temperature. The Vinyl Siding Institute says to leave about ¼ inch of clearance in every channel and about 1/32 inch between the nail head and the siding, so panels can slide. Nailed tight, it buckles in summer.
- Flash before you side. Windows and doors need flashing tape and a head flashing that sheds water onto the face of the wrap, not behind it.
- Mind the clearances. Keep fiber cement and engineered wood off the ground, roofs and decks by the gaps in the maker's install guide. Ignoring them is the usual reason a warranty claim is denied.
- Cut fiber cement safely. Cutting it releases crystalline silica. OSHA rules for crews call for shears or a saw with dust collection, outdoors. Homeowners should do the same and wear a respirator.
- Order from one batch. Colors drift between production runs. Buy all the siding and some spare at once.
- Check for lead. In homes built before 1978, removing painted siding or trim can release lead dust. The EPA requires contractors who disturb more than 20 sq ft of painted exterior on these homes to be lead-safe certified.
Vinyl is the most DIY-friendly siding: light, cut with snips, and forgiving. Fiber cement is heavy, often a two-person lift, and needs silica control. Anything above one story means scaffolding or pump jacks. Many owners hire out the high walls and gables and do the rest.
Common questions
What is a square of siding?
A square is 100 square feet of wall coverage. Siding is priced and ordered by the square, so a house with 2,500 square feet of wall needs 25 squares before waste. Most vinyl siding comes in boxes of 2 squares.
How many squares of siding do I need for a 2,000 square foot house?
A two-story house with a 2,000 square foot floor plan, about 40 by 25 feet, has roughly 2,300 to 2,500 square feet of wall after windows and doors. With 10 percent for waste, plan on about 25 to 28 squares.
How much does it cost to side a house?
Installed siding usually costs $3 to $12 per square foot for vinyl and $5 to $14 for fiber cement. The 2025 Cost vs. Value report puts an average vinyl siding replacement at about $18,000 and fiber cement at about $21,500.
How much extra siding should I order for waste?
Order about 10 percent extra for a simple house and 15 percent or more for many gables, dormers, bays or wood siding. Cut-offs at windows, gables and corners add up fast, and a matching color can be hard to find later.
Do I need house wrap under siding?
Yes. Building codes require a water-resistive barrier behind exterior siding, such as house wrap or felt, lapped so water runs down and out. Siding sheds most rain, but some always gets behind it.
Which siding lasts the longest?
Fiber cement can last 50 years or more with repainting every 10 to 15 years. Vinyl needs no paint and usually carries a lifetime limited warranty for the first owner. Engineered wood and real wood last decades if the paint and caulk are kept up.
Sources and assumptions
Prices are U.S. figures checked in October 2026. The main siding price can be edited; trim and wrap prices are fixed at the values below.
- Material prices from Menards, October 2026: double 4-inch vinyl $8.29–$12.49 per 12 ft 6 in panel; 5/16 x 12 ft fiber cement lap $14.99 (textured) to $26.99 (smooth); LP SmartSide 3/8 x 8 x 16 ft lap $16.99 primed, $19.99 prefinished; 11/16 x 8 x 14 ft red cedar bevel $38.99; vinyl J-channel $6.49–$7.98; 10 ft vinyl outside corner $17.49–$25.88; vinyl starter $4.99; 9 x 100 ft house wrap $82.67; 16 in x 12 ft vinyl soffit $24.99; fiber cement 5/4 x 4 x 12 ft trim $22.78; LP 1 x 4 x 16 ft trim $30.58; steel corner trim $24.37 and steel starter $6.99 per 10 ft; 5 lb of galvanized siding nails $24.99.
- Installed cost per sq ft by material and labor ($1–$4 per sq ft): Fixr, cost to replace siding, January 2026. Fiber cement lifespan and repainting interval: Fixr, fiber cement siding cost.
- Tear-off at $0.70–$2.00 per sq ft and fiber cement labor: This Old House, fiber cement siding cost, April 2026.
- Cost vs. Value 2025 job costs and resale recoup for vinyl and fiber cement, and maintenance notes by material: Consumer Reports siding buying guide (September 2026), citing the JLC Cost vs. Value 2025 report.
- LP SmartSide 5/50-year limited warranty: LP Building Solutions.
- Vinyl clearances (¼ inch in channels, about 1/32 inch at the nail head): Vinyl Siding Institute, Installation Quick Tips.
- Silica control when cutting fiber cement: OSHA, silica in construction. Lead-safe rules: EPA Renovation, Repair and Painting Program. Water-resistive barrier: International Residential Code, chapter 7.
- Assumptions: openings of 15 sq ft per window, 21 per door and 112 per garage door; J-channel or trim around each window (16 ft), door (17 ft) and garage door (30 ft), plus eaves and gable rakes, with 10% extra; eaves on the two long walls of a gabled house and all around a hip roof. Our estimates: steel siding at $4.25 per sq ft (piece length not listed; Fixr, updated April 2026, gives coated steel at $7 to $16 per sq ft installed but no material-only price), cedar trim at $24 per 12 ft board, starter for lap siding at $5 per 12 ft, steel J-channel at $12 per 10 ft, house wrap tape $12 per roll (one per wrap roll), aluminum fascia $15 per 12 ft, nails at about 1 lb per square. Soffit assumes overhangs up to 16 inches. The installed range uses Fixr's per-square-foot range for each material, but never less than our material total plus $1 to $4 per sq ft of labor, plus tear-off when checked.