Siding Calculator

Estimate siding squares needed for your walls

Total wall length (feet)

Wall height (feet)

Door/window area to subtract (sq ft)

Waste factor (%)

Frequently Asked Questions

What is a "square" of siding? ▼

A square is the standard unit siding is sold in: 100 square feet of wall coverage, regardless of the brand or panel size. It's a holdover from roofing terminology that the siding industry also uses.

How do I account for doors and windows? ▼

Subtract the total area of doors, windows, and other openings from your gross wall area before entering it here — this calculator doesn't automatically detect openings.

How much waste factor should I use? ▼

10% is a common default for straightforward rectangular walls. Complex walls with lots of corners, gables, or cuts around windows often need 15-20% to account for extra trim waste.

How many pieces come in a box? ▼

It depends on the manufacturer and panel size — vinyl siding boxes commonly cover about 1-2 squares each, but always check the specific product's coverage-per-box rating before ordering, since it varies.

How siding is measured

Wall area = total wall length × wall height
Net area = wall area − doors and windows
Squares = net area ÷ 100 (one square of siding covers 100 sq ft)
Order = squares × (1 + waste %)

Example

A house with 150 feet of walls that are 9 feet high has 1,350 sq ft of wall. Subtracting 100 sq ft of doors and windows leaves 1,250 sq ft, or 12.5 squares. With 10% waste, order 13.8 squares.

Don't forget the gables

A triangular gable end adds ½ × width × height. A 30-foot-wide gable that rises 8 feet adds 120 sq ft (1.2 squares) per end, so a house with two gables needs 2.4 more squares. Add them to the total wall area before calculating.

Openings and waste

A typical entry door is about 20 sq ft, a garage door 112 to 128 sq ft and a standard window 12 to 15 sq ft. Many installers subtract only large openings, since cutting around small windows creates waste anyway.

House shape	Waste factor
Simple rectangle	10%
Several corners, dormers or gables	15%
Complex design, many angles	20%

Trim and accessories

Siding is only part of the order. Measure separately in linear feet:

Outside and inside corner posts (each corner height)
J-channel around windows, doors and along the roofline
Starter strip along the bottom of every wall
Soffit and fascia under the eaves
House wrap, which covers the full wall area including openings

Material types

Vinyl is the cheapest and needs little maintenance; fiber cement (such as HardiePlank) costs more but resists fire and impact and can be painted; engineered wood falls in between. Fiber cement planks are sold by the piece, so convert squares to pieces using the exposure listed by the maker.

For the trim, use the linear foot calculator. If you are painting instead, the paint calculator gives gallons, and for the roof, the roofing calculator works in the same squares.