Property Repair Calculators

Siding Calculator

Siding is ordered in squares: one square covers 100 sq ft of wall. [1] Measure each wall up to the eaves, add the triangle at each gable end, deduct only large openings like garage doors, add 10% for waste, and divide by 100.

Results

Siding squares to order

1,510 sq ft with waste · 1 square = 100 sq ft

Wall area: 1,260 sq ft
Gable ends: 225 sq ft
Openings deducted: −112 sq ft
Net siding area: 1,373 sq ft
With 10% waste: 1,510 sq ft
Squares: 15.1 → 16

Panels come in boxes that cover a set area (often about 1 or 2 squares). Check the box coverage for your product, and order trim (J-channel, corners, soffit) separately by linear foot.

How this was calculated

Walls = 1,260 sq ft
Gable rise = 30 ÷ 2 × 6/12 = 7.5 ft
Gables = 2 × ½ × 30 × 7.5 = 225 sq ft
Openings = 112 sq ft
Net = 1,485 − 112 = 1,373 sq ft
With 10% waste = 1,510.3 sq ft
Squares = 1,510.3 ÷ 100 = 15.1 → 16

Worked example

A 40 × 30 ft one-story house with 9 ft walls, two gable ends on the 30 ft sides with a 6/12 roof, and a 16 × 7 ft garage door.

Walls:   2 × (40 × 9) + 2 × (30 × 9) = 1,260 sq ft
Gables:  rise = 30 ÷ 2 × 6/12 = 7.5 ft
         2 × ½ × 30 × 7.5 = 225 sq ft
Garage:  16 × 7 = 112 sq ft
Net:     1,485 − 112 = 1,373 sq ft
Waste:   × 1.10 = 1,510.3 sq ft
Squares: 1,510.3 ÷ 100 = 15.1 → 16

How the formula works

wall area   = Σ length × height (to the eaves)
gable area  = ½ × width × rise, where rise = width ÷ 2 × pitch ÷ 12
net area    = walls + gables − large openings
squares     = net area × (1 + waste %) ÷ 100, rounded up

The gable formula is the one the Vinyl Siding Institute gives for estimating (½ × height × width). [1] This is the vertical triangle of wall, not the roof surface; use the Roof Square Calculator for roofing.

Limitations

Siding squares are a surface area. Panels, trim, J-channel, corners, soffit, and fascia are ordered separately and are not included.
Box coverage varies by product and profile. Convert squares to boxes with the coverage printed on your product.
Dormers, bay windows, and multi-level walls need each surface entered as its own rectangle or gable.
Vertical siding waste depends on wall height versus panel length, so 10% may not be enough.
For insurance claims, matching rules for siding vary by state and policy. The quantity here is not a statement of what a policy will pay.

Common scenarios

Hail or wind damage on one side: enter only the damaged elevation. Whether undamaged sides are replaced for matching depends on your policy and state rules.
Two-story house: enter each wall at its full height to the eaves, and add any gables on the upper story.
Hip roof: set the gable count to 0; the walls go straight up to the eaves on all sides.
Checking an estimate: estimates usually list siding in squares (SQ). Compare that number with the squares here before waste to see how much waste the estimate includes.

Common questions

How many square feet is a square of siding?

One square is 100 sq ft. The Vinyl Siding Institute and LP both use this unit for ordering.

Should I subtract windows and doors?

The Vinyl Siding Institute says windows and doors are usually not deducted, because the extra acts as a waste allowance. Very large openings such as garage or sliding doors can be deducted.

How much waste should I add for siding?

The Vinyl Siding Institute says to add 10 percent to all material estimates for waste. LP suggests 5–10% extra.

How do I measure a gable end?

Measure the width at the base of the triangle and the roof pitch (or the height from the eave line to the peak). The area is half the width times the height.

Does this include soffit and trim?

No. Soffit, fascia, J-channel, and corner posts are measured in linear feet and ordered separately.

Sources and methodology

Squares, waste, and opening guidance come from the Vinyl Siding Institute installation manual and LP. This page is quantity only: it uses no prices.

[1] Vinyl Siding Institute — Vinyl Siding Installation Manual (2020). Retrieved 2026-09-25. VSI: “Every 100 square feet (9.29 square meters) is called a ‘square’ for ordering purposes.” LP: “One unit of siding (one square) is equal to 100 square feet.” VSI: “Add a factor of 10 percent to all material estimates to allow for waste.” LP suggests 5–10% extra. VSI: “Windows and doors are not usually deducted. Including them will provide an allowance factor for waste. If the windows and doors are extremely large (such as a garage or sliding glass doors), some deductions can be made.” VSI gives the gable area as ½ × height × width.
[2] LP Building Solutions — How to measure for siding. Retrieved 2026-09-25. LP: one square of siding is 100 sq ft; add 5–10% extra to account for mistakes.

This tool provides an educational estimate only. Insurance companies, contractors, and building officials may calculate these figures differently depending on policy language, property condition, local pricing, and applicable codes.

Disclaimer: Calculators and information on this site are provided for educational and estimating purposes only. Results do not determine insurance coverage, claim payments, repair requirements, or professional recommendations.