How do I calculate how much siding I need?

Measure the width and height of each exterior wall and multiply to get the area. Add the area of any gable ends (width × height ÷ 2). Subtract the area of doors and windows. Then add 5-15% extra for waste (cuts, defects, mistakes) and divide by 100 to convert to squares. Our calculator handles all these steps automatically — just enter your wall dimensions.

How do I calculate siding square footage?

For each rectangular wall, multiply width by height. For triangular gable ends, multiply width by height and divide by 2. Sum all wall and gable areas, then subtract door and window openings (width × height each). The result is your net siding square footage. Add 5-15% for waste to get the total square footage to order.

What is a 'square' of siding?

A square is the standard unit for selling siding and equals 100 square feet of coverage. For example, if your house needs 1,500 square feet of siding, you'll need to order 15 squares. Most siding panels and boxes are labeled by how many squares they cover.

How much does vinyl siding cost per square foot?

Vinyl siding typically costs $2.00 to $4.00 per square foot installed, including materials and labor. Materials alone average $1.50 to $2.50 per square foot, or about $150 to $250 per square. Premium or insulated vinyl can run $4.00 to $6.00 per square foot installed. Your total cost depends on house size, complexity, and local labor rates.

How much does Hardie board siding cost?

James Hardie fiber cement siding costs $5.00 to $9.00 per square foot installed. Materials alone average $2.00 to $3.50 per square foot ($200-$350 per square). Installation is more expensive than vinyl because Hardie board is heavier and requires specialized cutting tools. A 2,000 square foot house typically costs $10,000 to $18,000 for full Hardie siding replacement.

How do I calculate siding for gable ends?

Gable ends are triangular, so the area is half of a rectangle: measure the width of the gable at its base and the height from the base to the peak. Area = (width × height) ÷ 2. For example, a gable that's 20 feet wide and 6 feet tall has an area of 60 square feet. Add this to your wall area before subtracting openings.

How much extra siding should I buy for waste?

Most contractors recommend adding 10% extra for waste on standard jobs. For complex houses with many gables, dormers, and angles, add 15%. For simple rectangular houses with few openings, 5-7% may be sufficient. The material also matters — wood siding typically requires 15% waste due to knots and defects, while metal siding works with 5% because it produces less scrap.

How do I measure doors and windows for siding?

Measure the rough opening width and height of each door and window (the framed opening, not the door or window itself). Multiply width by height to get the area to subtract. A standard exterior door (36″×80″) is about 20 square feet. A typical window (36″×48″) is about 12 square feet. Don't subtract the trim area — siding goes up to the trim, not under it.

Siding Calculator

Units

Siding Material

Walls

4 walls

Wall 1

Width

Height

Wall 2

Width

Height

Wall 3

Width

Height

Wall 4

Width

Height

Gable Ends

Add triangular gable sections (area = width × height ÷ 2).

Doors & Windows

Subtract openings from total siding area.

Waste Factor

10% — for cuts, defects, and mistakes (Vinyl Siding default: 10%)

10%

Cost Estimate

Calculate material and labor costs for your siding project.

Total Siding Needed

Vinyl Siding · 10% waste

7.04

squares (704 ft²)

Area Breakdown

4 walls · Vinyl Siding

Wall Area

640.0ft²

4 walls

Net Area (Before Waste)

640.0ft²

Waste Added (10%)

+64.0ft²

Cuts, defects, and mistakes

Accessories Estimate

Trim and accessories needed with 10% waste

Starter Strip88 ft

Corner Posts36 ft (4 corners × 8 ft)

What Is a Siding Calculator?

Estimate how much siding you need in squares and square feet, plus material costs and accessories

A Siding Calculator helps homeowners and contractors estimate how much siding material is needed for an exterior siding project. By entering your wall dimensions, gable measurements, and door/window openings, the calculator determines the total square footage, converts it to siding squares (1 square = 100 sq ft), applies a waste factor for cuts and mistakes, and estimates material and labor costs.

Material Types

100 ft²

Per Square

$2–6

Per Sq Ft Installed

5–15%

Waste Factor

Whether you're installing vinyl, Hardie board, wood, or metal siding, this calculator covers all major materials with material-specific waste factors and default pricing. It also estimates essential accessories including starter strips, J-channel, corner posts, and drip cap.

How Is Siding Calculated?

The step-by-step formula for estimating siding material

Total Wall Area

Wall Area = Σ (Width × Height) for each wall

Sum the area of all exterior walls. For example, four walls at 20′ × 8′ = 640 ft².

Add Gable Areas

Gable Area = Σ (Width × Height ÷ 2) for each gable

Triangular gable ends are half the rectangle area. A 20′ wide gable with 6′ height = 60 ft².

Subtract Openings

Net Area = Wall Area + Gable Area − Opening Area

Subtract doors and windows. A standard 36″×80″ door = 20 ft².

Apply Waste & Convert to Squares

Total = Net Area × (1 + Waste%) → Squares = Total ÷ 100

Add 5-15% for cuts and waste. Then divide by 100 to get squares (the unit siding is sold in).

Example: Simple 4-Wall House

4 walls, each 20′ W × 8′ H = 640 ft² wall area
2 gables, each 20′ W × 6′ H = 120 ft² gable area
1 door (20 ft²) + 4 windows (15 ft² each) = 80 ft² openings
Net area: 640 + 120 − 80 = 680 ft²
With 10% waste: 680 × 1.10 = 748 ft² → 7.48 squares

Types of Siding Materials

Compare costs, durability, and maintenance for each siding option

Vinyl Siding

$2–4/ft² installed

+ Low maintenance, affordable, wide color range. − Can crack in extreme cold, fades over time.

Fiber Cement (Hardie)

$5–9/ft² installed

+ Fire-resistant, rot-proof, looks like wood. − Heavy, requires special cutting tools.

Wood (Cedar/Pine)

$6–12/ft² installed

+ Natural beauty, can be repainted. − Requires regular maintenance, insect and rot risk.

Metal (Aluminum/Steel)

$4–8/ft² installed

+ Fireproof, low maintenance, recyclable. − Can dent, limited color options.

Engineered Wood (LP)

$3–7/ft² installed

+ Wood look at lower cost, treated for pests. − Moisture-sensitive at cut edges.

Siding Estimation Tips & Common Mistakes

Avoid these common errors when measuring and ordering siding

Always measure twice

Double-check all wall measurements before calculating. A 1-foot error on a 20-foot wall means 8+ square feet per wall.

Don't skip the waste factor

Even professional installers order 5-10% extra. Complex jobs with many gables and openings need 15% or more.

Account for accessories

Starter strips, J-channel, corner posts, and drip cap add 10-20% to material costs. Our calculator estimates these automatically.

Consider your climate

Wood siding needs more maintenance in humid climates. Metal can dent in hail-prone areas. Fiber cement performs well in most conditions.

Check local building codes

Some jurisdictions require specific siding types or fire ratings. Always verify code requirements before ordering materials.

Frequently Asked Questions

Common questions and detailed answers

The essential siding accessories include: starter strip (goes at the bottom to lock in the first row), J-channel (goes around windows and doors to receive siding ends), corner posts (inside and outside corners), under-sill trim (goes under windows to hold siding in place), and drip cap/flashing (goes above windows and doors for water protection). Our calculator estimates quantities for all these items.

For a whole house, measure every exterior wall (width × height), add all gable areas (width × height ÷ 2), subtract all door and window openings, then add 10% for waste. Divide the total by 100 to get squares. For a typical 2,000 sq ft two-story home, expect 1,500 to 2,000 sq ft of siding (15-20 squares) depending on window and door coverage. Our calculator lets you add multiple walls and openings for complete house estimates.

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Last updated May 18, 2026

Siding Calculator

Area Breakdown

Accessories Estimate

What Is a Siding Calculator?

How Is Siding Calculated?

Types of Siding Materials

Siding Estimation Tips & Common Mistakes

Frequently Asked Questions

Embed Siding Calculator

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