Siding Calculator — Vinyl, Fiber Cement, Wood Lap

A siding calculator converts wall geometry into squares and trim runs: gross wall area (perimeter × height, plus gable triangles for 4/12 roofs), minus 14 sq ft per window and 20 sq ft per door, times a 10% waste factor, divided by 100 to get squares. Trim is measured in linear feet — J-channel around every opening's perimeter, starter strip along the bottom, and F-trim where siding meets soffits. One square always equals 100 square feet of covered wall, which is the unit every manufacturer's coverage chart and every contractor's bid uses.

A typical 2,000 sq ft two-story house (about 46 × 26 ft footprint, 18–19 ft of stacked wall height, 8 windows, 2 doors) needs 26–31 squares of siding — roughly 2,700 net square feet of wall after openings, plus 10% waste. The living-area number is not the siding number: siding scales with perimeter and height, so a sprawling single-story 2,000 sq ft ranch can need 35+ squares while a compact two-story needs 26. Run your actual footprint above rather than multiplying floor area.

Vinyl siding is boxed at about one square (100 sq ft of coverage) per box, so boxes ≈ squares after the 10% waste factor: a 28-square house takes 28 boxes. Always confirm the coverage printed on the specific box — double 4″ and dutch-lap profiles cover 100–120 sq ft per box depending on the manufacturer, and ordering against the printed coverage instead of a generic 1:1 rule is how installers end up 2–3 boxes short at 5 pm on sheathing day.

Budget 14 linear feet of J-channel per standard 3×4 window and 20 linear feet per 3-foot door, then add 10% for splices and mitered corners — the calculator above does exactly this. A house with 8 windows and 2 doors consumes 152 linear feet of J-channel, which at typical 12-ft-6 stick lengths is 13–14 pieces. Underspecifying J-channel is the most common trim error in DIY siding orders because it is invisible until the openings are actually trimmed.

Installed siding runs $295–$510 per square for vinyl, $570–$870 for fiber cement, $680–$1,020 for cedar lap, and $460–$720 for engineered wood at 2026 big-box-led reference pricing (material plus labor). Material-only, halve those figures. Vinyl earns the value benchmark: it installs in roughly half the labor hours of fiber cement, which is why its labor band starts at $200 per square while fiber cement starts at $350.

Yes — deduct 14 sq ft per standard window and 20 sq ft per door, as this calculator does. But keep the waste factor at 10% instead of dropping it: the cutoffs around every opening produce offcuts that rarely fit the next wall, and trim consumes its own offcuts too. Deducting openings and keeping full waste lands within one square of a professional takeoff on typical houses; skipping the deduction overshoots by 2–3 squares, and skipping waste undershoots by the same margin.

The math favors fiber cement when you plan to stay 15+ years: it costs roughly $280 more per square installed (a $5,600 premium on 20 squares) but holds a paint finish 15–25 years versus vinyl's fade-and-crack cycle, and it resists hail and wind-blown debris that embrittles vinyl. For a 5–10 year horizon, or a rental where refresh cost dominates, vinyl's $295–$510 per square installed wins on total spend. Engineered wood splits the difference at roughly 60% of cedar's cost with a wood-look finish.

This page uses the same units big-box stores quote in — squares, boxes, and linear feet of trim — with reference price bands modeled on 2026 in-store product ranges rather than a single day's web price. Store prices move weekly and vary by region and profile, so treat every dollar figure here as a calibration band: if a local quote or shelf price sits more than 20% outside the band shown for your material, something differs — profile, insulation backing, or scope — and it's worth asking which.