Siding Calculator

Last Updated: May 2026

Error: Window/Door area cannot be larger than the total wall area.
1. Rectangular Walls
2. Gables (Triangular Areas)
3. Windows & Doors (To Subtract)
4. Siding Specifications
10%
10% is standard. Use 15% for gables and complex cuts.
5. Price (optional)
$
Enter a valid price.
Results: Siding Required
Total Siding Squares Needed
–
1 Square = 100 sq ft. Includes 10% waste.
–
Total Boards / Pieces
–
Gross Sq Ft (with waste)
–
Net Sq Ft (exact area)
Estimated Material Cost
–

Ordering the wrong amount of siding leads to terrible color lot mismatches or wasted money. You need exact numbers before you spend a single dollar. This calculator outputs your exact net square footage, gross square footage, total siding squares, true board count, and a reliable material cost estimate. It works for vinyl siding, fiber cement, wood lap, and custom profiles. Stop guessing your numbers. Plug your measurements in below and get your exact takeoff instantly.

How to Use This Siding Calculator

Step 1: Enter Your Rectangular Walls

Measure each wall face as a solid rectangle. Just multiply the linear feet of length by the height in feet. Do not subtract windows yet; the calculator handles that part separately later. Add as many exterior wall dimensions as your house has faces by clicking the “+ Add Another Wall” button.

Step 2: Add Gable Areas (If Any)

Gables are the triangular wall section located just underneath a roof pitch. Enter the base width and the vertical height from that base up to the peak. The calculator handles the gable area calculation automatically using the standard trade math (Base × Height ÷ 2). If your house does not have a gable end, simply skip this block.

Step 3: Enter Windows and Door Openings

Measure the width and height of every major opening. The calculator subtracts these window exclusions and door openings from your total. This gives you a true net wall area instead of a padded-up rough estimate.

Step 4: Choose Your Siding Type

Select your material from the dropdown. Options include Double 4″ vinyl, Double 5″ vinyl, James Hardie fiber cement (7″ exposure), and Custom Siding Board. If you select the custom siding profile, you must enter the exposure width in inches and the board length in feet manually. The calculator converts this specific panel profile into square feet per board automatically.

Step 5: Set Your Waste Factor

Move the slider to set your waste. The default sits at 10%. You should adjust this up to 15% or higher if your house has multiple gables, lots of angles, or if you are a first-time installer. This accounts for material waste, normal cut-off waste, and a safe waste allowance.

Step 6: Enter Your Material Price (Optional)

Enter your local material price and choose if it is a price per square or price per board. The calculator outputs your total material cost estimate. Leave this field blank if you are only doing a quantity takeoff.

Step 7: Read Your Results

The result box shows your exact numbers: net square footage (the actual wall area), gross square footage (with waste added), total siding squares to order, total board count, and the estimated material cost.

How to Measure Your House for Siding (The Contractor Method)

This is what a siding crew does on the first morning of a new job. Grab a 100-ft tape measure, a notepad, and maybe a chalk line. You need to break the entire house down into simple shapes, mostly rectangles and triangles. If a two-story house has stories that change height or walls that step back, break that wall into two separate rectangles.

Measuring Rectangular Walls

Take your wall face measurement starting from the bottom plate up to the soffit. This gives your exterior wall height. Multiply this by the length of the wall. Walk the entire building perimeter and record each rectangular face separately.

Measuring Gable Ends

A gable end wall is a triangle. Measure the base width first. Then, measure the exact vertical peak height starting from the bottom base line straight up to the roof peak. Never measure along the roof slope. That is a common beginner mistake. The triangular area of this rake wall is always (Base × Height) ÷ 2.

Pro Tip: On a very steep pitch, use a level and tape to measure the true vertical height. Do not use a rolling measuring wheel against the sloped edge.

Accounting for Windows, Doors, and Other Openings

Measure the rough opening of every window and door. Write down every window exclusion and door exclusion. You must subtract these to get your true net area. A standard 16×7 ft garage door is 112 sq ft. If you do not subtract it on a small wall face, your entire material estimate becomes completely wrong.

Measuring Around Bay Windows and Bump-Outs

A bump-out or a bay window actually has three separate wall faces. Each side needs its own siding. You must account for every outside corner and inside corner here because they use up material and create extra offcuts.

What Is a Siding Square?

A siding square equals exactly 100 square feet of wall coverage area. Siding suppliers use the exact same unit as a roofing square because it makes pricing, stocking, and shipping large material orders much easier.

Most siding comes in packages where the carton coverage equals exactly 1 or 2 squares. Knowing your total squares helps you buy in even carton multiples so you do not open extra boxes needlessly.

  • 600 sq ft = 6 squares
  • 1,350 sq ft = 13.5 squares
  • 2,000 sq ft = 20 squares

Exposure Width vs. Actual Board Width — Why This Number Changes Everything

You cannot use the full actual width of a board to calculate your numbers. Lap siding overlaps. The top edge of the lower board hides behind the bottom edge of the board above it.

The part you actually see is the exposure width. Installers also call this the face width, reveal, or course width. Your true board count is calculated on gross area ÷ square footage per board. The square footage per board is:

(exposure width in inches × board length in feet) ÷ 12.

Vinyl Siding — Double 4″ Profile

  • Each panel shows two 4″ courses. This equals 8 inches total exposure per panel.
  • Standard panel length: 12 ft.
  • Coverage per panel: (8 in × 12 ft) ÷ 12 = 8 sq ft per panel.
  • Panels per square: 100 ÷ 8 = 12.5 panels.

Vinyl Siding — Double 5″ Profile

  • Each panel shows two 5″ courses. This equals 10 inches total exposure per panel.
  • Standard panel length: 12 ft.
  • Coverage per panel: (10 in × 12 ft) ÷ 12 = 10 sq ft per panel.
  • Panels per square: 100 ÷ 10 = 10 panels.

Fiber Cement — James Hardie HardiePlank (7″ Exposure)

  • Actual board width: 8.25 inches.
  • Standard overlap: 1.25 inches.
  • Exposure width: 7.0 inches.
  • Standard board length: 12 ft.
  • Coverage per board: (7 in × 12 ft) ÷ 12 = 7 sq ft per board.
  • Boards per square: 100 ÷ 7 = ~14.3 boards (always round up to 15).

Custom Siding Profiles

If you install LP SmartSide, cedar bevel siding, Miratec trim, or another profile, just enter the exposure width and board length manually into the calculator. The math stays exactly the same.

Important Note: Different regions and different product lines have different overlap rules. Always read the installation guide for your specific material. The installation guide controls your warranty compliance, not the simple spec sheet.

How Much Waste Factor Should You Add?

Your waste factor is not just a buffer for mistakes. It is mostly cut-off material that falls to the ground. Even a 20-year veteran installer generates waste. The waste percentage slider goes from 0% to 25%. Here is how to pick the right number.

10% Waste — When It Works

Use this for a simple rectangular house with no gables, few windows, and one story. It assumes an experienced installer making clean cuts. On a 1,000 sq ft net area, a 10% waste equals 100 extra sq ft (about 14 additional fiber cement boards).

15% Waste — The More Common Reality

Use this for almost any house with gable ends. Gable waste is high because angled cuts leave irregular triangle shapes that you cannot reuse easily. Use 15% if you have bay windows, lots of trim transitions, or if you are a DIY installer. On a 1,000 sq ft net area, 15% equals 150 extra sq ft.

20%+ Waste — Specific Situations

Use 20% or more for complex rooflines with multiple intersecting gables. If you do a diagonal installation or herringbone pattern, your waste goes very high. You also need a higher number if color lot or dye lot matching is critical. You want enough material overage from the exact same factory batch to cover future repairs.

Pro Note: Some siding contractors skip subtracting windows entirely and just use those empty spaces as their built-in waste buffer. This works roughly on a basic house. It fails totally on a wall with 40% glass. Always subtract your exclusions cleanly, and apply a separate waste factor. Your numbers will be much more accurate.

Siding Materials This Calculator Handles

Double 4″ Vinyl Siding

This is a standard budget-friendly siding. A vinyl panel with a double 4 profile is very common on mid-range residential homes. The panels are typically 12 feet long, and standard carton coverage usually packages 2 squares per box.

Double 5″ Vinyl Siding

This gives a wider exposure and a slightly more upscale look. A mid-range vinyl with a double 5 profile uses the same 12-foot length, but because it covers more area per piece, you only need 10 panels per square.

James Hardie HardiePlank (Fiber Cement)

This is the standard fiber cement lap siding. The calculator uses the normal 8.25″ cement board with a 7″ exposure. James Hardie makes an HZ5 board for cold climates and an HZ10 board for warm areas. This climate difference only changes the factory primer, it does not change the physical board dimensions.

Custom Profile

Use this for engineered wood siding like LP SmartSide, any composite siding, traditional cedar bevel, or any custom siding profile. You just provide the exposure width and board length.

How to Estimate Siding Material Cost

Your material cost estimate changes entirely depending on where you buy. Suppliers use two different pricing models.

Per-Square Pricing (Pro Supply Houses)

A pro supply house or local lumberyard sells by the square.

  • Fiber cement: Roughly 70–120 per square (material only).
  • Vinyl: Roughly 100–180 per square (depends on profile/brand).

Per-Board Pricing (Big Box Retail)

A big box retail store like Home Depot or Lowe’s sells mostly by the individual piece.

  • James Hardie boards: 8–14 per board.
  • Vinyl panels: 1.50–4.00 per panel.

Regional Pricing Variation

Prices in the Northeast, Pacific Northwest, or Gulf Coast will differ due to freight and local demand. Treat the calculator’s dollar output as a baseline materials-only estimate to anchor your contractor bid conversations.

What This Siding Calculator Does Not Calculate

This tool calculates your main siding field panels. You still need to calculate and buy:

  • Trim boards: Corner posts, J-channels, window trim, and soffit trim need a separate linear footage calculation.
  • Starter strips: Required at the base of the bottom wall. Measured in linear feet.
  • House wrap / WRB: Tyvek or similar wraps are measured in sq ft but sold in large rolls.
  • Fasteners and nails: Fiber cement needs hot-dipped galvanized or stainless nails. Count depends on stud spacing.
  • Labor cost: Labor normally runs 1.50–1.50–5.00 per sq ft depending on location and house difficulty.
  • Scaffolding or lift rental: Extra cost for two-story houses.
  • Moisture barrier tape and flashing: Required around every wall penetration by code.
  • Caulk and sealant: Required at butt joints and corners.
  • Paint or primer: If you buy primed-only boards, you must pay for field painting.

Frequently Asked Questions (FAQs)

How many squares of siding does an average house need?

The average single-story 2,000 sq ft ranch home has roughly 1,200–1,600 sq ft of exterior wall area. This equals approximately 12 to 16 siding squares, depending heavily on roof pitch, gable configuration, and window count. Two-story homes with the same foundation footprint typically have 20–28 squares. Use the calculator above for job-specific numbers.

What is the difference between net square footage and gross square footage?

Net square footage is the exact raw area of your walls minus your windows and doors. Gross square footage is that net area plus your chosen waste factor percentage. You must always order materials based on the gross number.

Can I use the window area as my waste factor instead of subtracting it?

Some contractors do this on very simple houses with average-sized windows. It is not recommended here because it falls apart completely on walls with large openings. A wall with a 16-ft garage door and two large picture windows could easily have 200 sq ft of exclusions. That is way more than a 15% waste factor on most walls. Subtract exclusions separately first, then add waste.

How many James Hardie boards are in a square?

For standard HardiePlank with a 7-inch exposure at a 12-foot length, one square requires approximately 14.3 boards. In actual practice, you order 15 boards per square to account for rounding and minor cutting waste. At a 7-inch exposure, one single board covers exactly 7 sq ft.

What is the correct overlap for fiber cement siding?

James Hardie specifies a strict minimum 1.25-inch overlap for HardiePlank. This leaves a 7-inch exposure on an 8.25-inch board. This rule is in the installation manual. Undershooting this overlap voids the warranty and leaves the top nailing flange exposed to water.

How do I measure a gable for siding?

Measure the base width of the triangle at its widest bottom point. Then measure the vertical height from that flat base line straight up to the peak. Do not measure along the angled roof slope—always measure the true vertical dimension. The area formula is (Base × Height) ÷ 2. The calculator does this part automatically.

Do I need more waste factor for gable areas?

Yes. Gable cuts are angled. The cut-off pieces are weird irregularly shaped triangles that rarely get reused on another part of the wall. A house with prominent gables warrants a 15% waste factor or higher. If your whole upper story is gabled, consider 18–20%.

How much does siding material cost per square?

Vinyl siding runs roughly 100 – 180 per square for the material. Fiber cement runs 70 – 120 per square for the bare boards, but requires you to buy nails, caulk, primer, and paint on top of that. Engineered wood (LP SmartSide) sits mostly between the two. Prices change by region, and pro supply houses beat big-box pricing on large orders.

What is a siding square?

One siding square equals exactly 100 square feet of wall area. It is the same standard unit used in roofing. Siding manufacturers package their products to cover exactly 1 or 2 squares per carton. All material takeoffs and supplier quotes use squares.

Does this siding calculator work for vertical siding or board-and-batten?

Yes. Just use the Custom Siding Board option. Enter the exposure width (the actual visible face width, not the full board width) and the board length. For board-and-batten jobs, the exposure is the full face of the flat board minus the batten strip overlap. The math is exactly the same for any vertical or lap coverage.

Do I need to add extra siding for future repairs?

It is very smart to keep 5–10% of your total order in a dry storage area, especially for fiber cement. Color matching across different factory batches is difficult. Manufacturers cannot guarantee dye lot consistency across orders placed years apart. If a tree branch breaks a board in five years, the new boards you buy might not match perfectly.

Sources & References

Other Similar Calculators

Qazi Raza Ul Haq - Developer of Expert Build Calc

About the Developer: Qazi Raza

Qazi Raza is a web developer and search engine optimization specialist who has spent years building programmatic calculators for real‑world construction, landscaping, and renovation projects. By combining engineering reference data with practical field standards, he designs tools that help homeowners, DIYers, and contractors estimate materials with confidence. Every calculator is built from verified density charts, compaction guidelines, and industry‑accepted formulas.