Siding Calculator
Calculate siding square footage, siding squares, vinyl cartons or exposed lap planks. Measure walls, roof-pitch gables, openings and supplier trim quantities, with optional material prices.
Enter measurements below. The result updates as you type.
Calculation breakdown
Wall area
Rectangles use width x height.
Gable area
Triangular gables use base x height / 2.
Net area
288 - 15 = 273 sq ft
Purchase area
273 sq ft plus 10% waste, then divided by coverage.
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Related calculators and guides
Open the project hub for nearby tools, measurement guidance, and published articles.
Formula explanation
Core siding estimate basis
Net siding sq ft = Σ(wall width × height × count) + Σ(gable width × rise ÷ 2 × count) − Σ(opening width × height × count). Siding squares = net sq ft × (1 + waste%) ÷ 100. Plank coverage = stock plank length × approved installed exposure; whole cartons = ceil(whole pieces ÷ pieces per carton).
- Use effective coverage per piece, or actual lap plank length times visible installed exposure; never use nominal overlapping board height as coverage.
- For a symmetrical gable at a rise-per-12 roof pitch, gable rise = half the base width × pitch rise ÷ 12.
- Final quantities must round according to the selected material unit.
- User-measured starter, J-channel and corner trim runs can be divided by entered stock lengths and rounded to whole pieces; geometry reference runs do not decide where accessories are required.
- Per-piece and per-carton material prices are independent supplier scenarios excluding tax, trim, labor and delivery; no installed-cost forecast is implied.
Worked example
Simple wall example
24 ft wide x 9 ft high wall, before openings
- 1Multiply width by height.
- 2Subtract supported doors and windows.
- 3Divide by product coverage after waste is added.
Gross wall area: 216 square feet, before deductions and waste.
Estimate assumptions
Check these assumptions before ordering
- Main walls, gables, and openings should be calculated as separate sections.
- Coverage depends on the selected siding product and exposure: lap planks require their approved installed visible reveal, not nominal face width.
- Optional roof pitch assumes a symmetrical triangular gable; measure the actual rise for asymmetrical or unusual roofs.
- Matching-section counts multiply the associated measured wall, gable, window or door dimensions.
- Supplier cartons, accessory stock lengths and prices must be entered; defaults do not invent packaging or local bids.
- Starter strips, J-channel and corner pieces are calculated only from user-entered measured run lengths and stock lengths; the geometry reference is not a universal accessory specification.
- House-wrap order uses gross facade surface plus entered overlap/waste and product-effective roll coverage; do not mistake it for a complete drainage or building-envelope design.
Measurement checklist
How to measure
- Measure each rectangular wall section by width and height.
- Measure triangular gables by base width and vertical height; alternatively enter a roof pitch as rise per 12 for a symmetrical gable.
- Group matching wall or opening sections using the correct whole-number quantity instead of repeatedly adding identical measurements.
- Measure windows and doors as opening width times height so they can be deducted.
- Use the actual coverage per individual piece, or choose exposed lap and enter plank length and installed reveal from the product label/manual.
- Enter pieces per carton, per-piece and per-carton supplier prices only when known; inspect accessory runs and trim lengths before ordering.
Avoid these errors
Common mistakes
- Forgetting that triangular gables use half of base times height.
- Deducting openings larger than the gross wall area.
- Confusing siding squares with square feet; one square is 100 square feet.
- Using nominal board width rather than installed lap reveal to calculate fiber-cement or wood-lap planks.
- Confusing the area-based minimum with a site-verified siding cut/stagger plan.
- Ordering accessories from opening and roof-rake perimeter geometry alone without checking the actual required trims and terminations.
Estimate disclaimer
Verify before ordering.
Use the output as a planning baseline. Site conditions, product coverage, waste, supplier units, installation method, and local requirements can change the final quantity.
Related calculators
Continue the same project estimate
Exterior Projects
Gable Siding Calculator
Measure the triangular siding wall below a gable roof, including symmetrical, off-center ridge and single-slope shed ends. Derive vertical rise from roof pitch where supported, calculate each sloping rake edge for trim stock, deduct gable openings and obtain real supplier package quantities and optional material-only quotes.
Exterior Projects
Siding Square Calculator
Decode a contractor or supplier quote in siding trade squares (100 square feet each), or use known wall area. Convert to net square footage, optional waste, unopened product-specific cartons and leftover coverage; compare user-entered material rates per trade square versus full box without inventing market prices.
Exterior Projects
Vinyl Siding Calculator
Convert a measured single wall or previously measured gross siding area into vinyl panel and carton quantities. Cross-check actual panel reveal against printed box coverage, see where a full-course order differs from ideal square footage and enter real supplier prices instead of guessed costs.
Exterior Wall Materials
Stucco Calculator
Calculate base-coat and finish-coat purchases separately. Deduct measured openings, use coverage for the specified coat thickness, and round each product only after combining its required quantities.
Published guides
Understand the measurements and assumptions
Supporting guide
How Much Siding Do I Need?
Add wall and gable areas, subtract openings, convert to siding squares or product coverage units, and apply a clear waste allowance.
Read guide
Supporting guide
Vinyl Siding Cost by House Size: Area, Squares, and Scope
Learn why house floor area is not siding area, then estimate vinyl siding cost from measured walls, siding squares, product coverage, and project scope.
Read guide
Common questions
Use the result with context
01Can I include triangular gables when calculating siding square footage?+
Yes. Add gable sections with base and height; the calculator uses base times height divided by two.
02How do I calculate horizontal lap siding by visible exposure?+
Measure the actual stock plank length and the installed exposed reveal in inches, not the nominal board height. The estimator multiplies plank length by visible exposure to find net installed coverage per plank, divides the waste-adjusted facade area by that coverage, then rounds up whole planks. Confirm overlap and fastening with the exact manufacturer manual.
03Can I estimate vinyl siding cartons and material costs?+
Yes. Enter the actual coverage per piece and pieces per full carton stated by the supplier. The calculator rounds first to whole pieces and then to full cartons. You can compare a loose-piece unit price and a separately entered full-carton price. Prices exclude tax, labor, delivery and accessories.
04Can I estimate siding in gables using a 6/12 roof pitch?+
For a symmetrical triangle, the gable rise equals half the gable base multiplied by 6/12, and its siding area is one-half of the base times that rise. The pitch entry replaces manually entered peak height for that gable only. Measure irregular or offset gables directly rather than assuming symmetry.
05Does siding trim include J-channel, starter strips and house wrap?+
The calculator shows wall-base, opening-perimeter and gable-rake reference lengths, but does not automatically treat every edge as a required accessory. Enter actual measured starter, J-channel and corner lengths plus product stock lengths to get whole pieces. Housewrap rolls require supplier effective roll coverage and a separate overlap allowance.
06Can siding coverage vary?+
Yes. Coverage is editable because profile, exposure, package size, and manufacturer data can vary.
07How many square feet are in one square of siding?+
One siding square covers 100 square feet. For example, 850 square feet of purchase area equals 8.5 siding squares; the calculator shows the square-footage and siding-square results after waste.
08Should I deduct windows and doors when measuring siding?+
Yes. Add the measured width and height of windows and doors to the openings section. The calculator deducts their area before applying waste; allow separately for trim and cut complexity.