Siding Calculator
Wall squares the way distributors count them — net of openings, waste-added, boxed by the 2-square carton, with the trim package counted separately.
Siding Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Rectangular walls — bumpays and turrets are entered as extra width.
- Opening deductions use 20/15 ft² standards, not your measurements.
- Soffit, fascia and corner-post lengths are prose, not fields.
In short: Four walls 1,400 ft² gross, minus two doors and six windows: 1,270 ft² net, 1,397 with 10% waste — 14 squares, 7 cartons, 140 ft of starter, 134.67 ft of J-channel. Priced at $100 a square plus $3.50/ft² labor on the net: $5,845.00.
Formula
net = walls + gables − doors × 20 − windows × 15
squares = ⌈net × (1 + waste%) ÷ 100⌉
cartons = ⌈squares ÷ 2⌉
cost = squares × $/square + net × $/ft² labor
[('square', '100 ft² of wall — how distributors price'), ('2 / carton', 'standard vinyl carton = 2 squares'), ('20 / 15', 'door / window ft² deduction defaults'), ('labor on net', 'waste inflates material only')]
Worked Example
- Add wall widths, multiply by height, add gable halves.
- Deduct 20 ft² per door, 15 per window.
- Add 10-15% waste; divide by 100 for squares.
- Halve for cartons; count starter and J-channel.
- Price squares plus net-area labor.
1,400 gross − 130 openings = 1,270 net; at 10% waste, 1,397 ft² → 14 squares → 7 cartons; trim: 140 ft starter + 134.67 ft J-channel; $100/square + $3.50 labor on net = $5,845.00.
Strengths & Limits Of This Model
Where this engine is strong
- Distributor's own unit — squares and cartons
- Trim package counted, not forgotten
- Labor on net — the quiet 10% bid-pad refused
Where it stops
- Standard opening sizes, not measured ones
- No panel-by-panel course layout
Practical Use Cases
Re-side bids
Square counts against distributor quotes.
DIY cartons
How many boxes to stack in the driveway.
Trim take-offs
Starter, J-channel, corner posts.
Insurance scopes
Net wall after openings.
Material swaps
Same squares, new $/square.
Methodology & Editorial Standards
Net wall = widths × height + gables − openings at 20/15 ft² defaults (free-entry counts). Waste inflates material only, at the entered 0-25%; squares ceil to the 100-ft² unit, cartons ceil at two squares. Trim counts starter at base width and J-channel at opening perimeters using the 3×6⅔ door / 3×5 window standards. Cost = squares × free-entry $/square + net × free-entry labor. Zero-area and waste > 25% refused.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Siding Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How do I calculate siding squares?
Wall area (width × height, plus ½ × base × height per gable) minus doors and windows, times (1 + waste%), divided by 100, rounded up. That is the unit every distributor quotes.
How many squares are in a box of vinyl siding?
Two — a standard carton covers 200 ft², roughly 20-24 twelve-foot panels depending on profile (double 4, double 5, dutch lap).
How much waste should I add?
10% on simple rectangles; 12-15% with dormers, bays and broken rooflines; 15-20% on ornate Victorians. Waste also covers panels damaged on the wall — do not run it at zero.
What is J-channel for?
It hides and receives the cut panel ends around windows, doors and soffit transitions. Count its perimeter: about 19.3 ft per 3×6⅔ door, 16 ft per 3×5 window.
How much does vinyl siding cost installed?
Vinyl runs roughly $4-13 per square foot installed by region and profile; labor alone averages $2.50-5.00 per foot². This page prices your quote, it asserts no band.
Why is labor priced on net area?
Crews hang panel over the wall that exists — the waste factor buys extra cartons, not extra hours. Pricing labor on the waste-inflated area quietly adds 10% to the bid.
Do gables count?
Yes — each gable is ½ × base × height. Two matching ends are just base × height total.
What is starter strip?
The hooked course that receives the first row of panels, run along every wall base — count it at the same linear footage as the wall widths you entered.