Siding Calculator: How Much Siding Do I Need?

How to measure a house for siding

The Vinyl Siding Institute’s installation manual breaks every house into rectangles and triangles, and this calculator follows the same steps.

1. Walls: add up the length of every wall you are siding, corner to corner, and measure the height from the bottom of the siding (just above the foundation) to the eaves. For a simple box, the length is the perimeter.
2. Gables: for each triangular gable end, measure its width at the eave line and its height from the eave line to the peak. A gable’s area is ½ × width × height.
3. Openings: leave ordinary windows and doors in. The manual’s advice is not to deduct them, because the cut-off around them is about equal to their area and works as a waste allowance. Deduct only very large openings such as garage doors and sliding glass doors.
4. Waste: the manual adds 10% to every material. Use more for houses with several gables, dormers or bump-outs.

Dormers are triangles too (½ × height × width for each side), and a gambrel gable splits into a trapezoid and a triangle. Add those areas into the gable fields as an equivalent, or work out the total and enter it as extra wall length at full wall height.

From square feet to squares, cartons and planks

Siding, like roofing, is ordered by the square: 100 sq ft of wall. How many pieces make a square depends on the product.

• Vinyl is sold in cartons. James Hardie’s conversion chart lists a common vinyl container as 2 squares, so the calculator rounds up to whole 2-square cartons. Check your brand’s label, since some profiles pack differently.
• Fiber cement lap siding comes in 12 ft planks, and each covers 12 ft × its exposure, the part left showing after the next course overlaps it. A 8¼ in plank laid at 7 in exposure covers 7 sq ft, so a square takes 100 ÷ 7 = 14.3 planks. That matches Hardie’s chart (143 pieces for 10 squares).
• Panels (for board and batten or plain vertical siding) are 4×8, 4×9 or 4×10 ft sheets. Battens go over the panels at 12 or 16 in on center; Hardie’s chart allows 3 battens per 4 ft panel at 16 in and 4 at 12 in, plus a starter batten.

Hardie’s chart rounds each single square up to whole planks (17 at 7¼ in, 13 at 9¼ in, 10 at 12 in); the calculator keeps the fraction until the end so a large wall is not over-counted. Wider planks mean fewer pieces and fewer courses to nail, which is part of why the 8¼ in plank is so common. The calculator applies the waste to the area before converting, then rounds up to whole pieces.

Starter strip, corners, trim and nails

Siding jobs run short on trim more often than on siding. The calculator lists each accessory separately, in linear feet and in 12 ft pieces, with the same waste allowance:

• Starter strip runs around the entire base of the house, so it equals the wall length you entered (VSI).
• Outside and inside corners are one wall height each. Vinyl uses a one-piece corner post; fiber cement corners are usually built from two trim boards, so they are doubled.
• Window and door trim (J-channel for vinyl, trim boards for fiber cement) uses Hardie’s figures: about 16 linear ft around a 3×5 ft window and 19 ft around a 6′8″ × 3′ door. Large picture windows and double doors take more, so add a window for each extra 3 ft of width.
• Gable rake trim follows both sloped edges of every gable, the sloped length worked out from the gable’s width and height.
• Fasteners. For vinyl, the VSI manual gives 0.01 lb of roofing nails per square foot of siding (0.005 lb if you use aluminum nails). Hardie’s chart estimates about 5,000 nails for a 30-square house.

Soffit and fascia are separate products measured along the eaves and are not included. Neither are house wrap and flashing, which most manufacturers require behind the siding.

Siding cost per square foot

HomeGuide’s installed ranges are national estimates that vary by region; it adds $0.70 to $2.00 per square foot to tear off the old siding and puts materials at 50% to 55% of the total. The price switch in the calculator multiplies your net wall area (before waste) by the range for the material you pick. When you are also replacing the roof, the roof replacement cost calculator prices that job in the same way, and the paint calculator covers repainting instead of re-siding.

How the price compares with other sources

The price lines use HomeGuide’s installed ranges by product, and the headline is their midpoint. Other sources read on Oct 27, 2026: HomeGuide $4 to $13 per sq ft across common materials, Modernize $8.60 per sq ft for mid-range siding ($17,200 for a 2,000 sq ft house), and Fixr a $14,500 average for a 2,000 sq ft home ($8,500 to $20,000), about $7.25 per sq ft.

These are national figures and prices vary by region, wall height and how much trim is involved.

Sources & assumptions

How this calculator gets its numbers. Full method: our methodology.

• Wall area = wall length × wall height; each gable = ½ × width × height (Vinyl Siding Institute). Ordinary windows and doors are not deducted, as the VSI manual advises, because the cut-off around them is about equal to their area; very large openings can be.
• Waste defaults to 10% (VSI) and is applied to siding, starter strip, trim and rake lengths. 1 square = 100 sq ft.
• Vinyl is counted in 2-square cartons; fiber cement planks are 12 ft long and cover 12 ft × the exposure, so pieces per square = 100 ÷ exposure in inches (James Hardie chart). Panels are 32, 36 or 40 sq ft; battens are 48 ÷ spacing per panel plus one starter batten per wall.
• Trim per opening comes from the James Hardie chart: 16 linear ft for a 3×5 ft window, 19 ft for a 6'8"×3' door. Corner trim is wall height per corner (two boards per corner for fiber cement), cut from 12 ft pieces.
• Vinyl fasteners: sq ft × 0.01 lb of roofing nails (VSI). Fiber cement: about 5,000 nails per 30 squares (James Hardie chart).
• Installed prices per sq ft are national estimates that vary by region, from HomeGuide (October 2025); old siding removal is $0.70–$2.00 per sq ft.

Sources

1. Fixr, How Much Does It Cost to Replace Siding? [2026 Data]. Updated Jan 23, 2026: $14,500 average for a 2,000 sq ft home, $8,500–$20,000 typical.
2. Modernize, Home Siding Cost Calculator. Updated Sep 23, 2026: $8.60 per sq ft installed for mid-range siding; worked example uses vinyl at about $6 per sq ft installed.
3. Vinyl Siding Institute / Polymeric Exterior Products Association, Vinyl Siding Installation Manual (2022). How to measure: walls height × width, gables ½ × height × width; windows and doors not usually deducted; starter strip = linear ft around the base; nails 0.005 lb (aluminum) or 0.01 lb (roofing nails) per sq ft; add 10% for waste; 100 sq ft = 1 square.
4. James Hardie (co-branded copy hosted by MRS Lumber), Measurement to Hardie Product Piece Count Conversion Chart (HS2090). 12 ft HardiePlank pieces per square by width/exposure (5.25/4 in: 25; 6.25/5: 20; 7.25/6: 17; 8.25/7: 15, 143 per 10 sq; 9.25/8: 13; 12/10.75: 10); panels 4×8, 4×9, 4×10; battens 3 per panel at 16 in o.c., 4 at 12 in, plus 1 starter; window and door trim lengths; ~5,000 nails per 30-square home.
5. HomeGuide, How much does siding cost?. $4–$13 per sq ft installed; by material: vinyl $4–$12, aluminum $6–$10, board and batten $5–$13, cedar $6–$16, engineered wood $7–$12, fiber cement $6–$15, steel $7–$16; old siding removal $0.70–$2.00 per sq ft.

Last reviewed October 27, 2026. Product figures vary by brand; the label on what you buy wins.