Siding Calculator
To work out how much siding you need, multiply the length of the walls by their height, add the gable triangles, subtract windows and doors, and divide by 100 for squares of siding. Add a waste allowance, then convert squares to pieces and boxes for the profile you buy: double 4 inch vinyl runs 12 pieces to the square and usually 2 squares to the box. Enter your house for the squares, pieces, boxes, trim and nails.
Your walls
All walls to be sided, end to end.
Ground or foundation to the eaves.
Triangles under the roof ends.
Across the base of each gable.
Sets the gable height.
A 3 x 5 ft window is 15 sq ft.
More for gables and angles.
Sets pieces per square.
Visible face of one board.
Length of one board.
Printed on the carton.
1,440 walls + 225 gables − 0 openings
with 10% waste
12 per square, double 4 in vinyl
at 2 squares per box
Ply Gem factors per square
1/3 lb per square
At $4 to $12 per square foot installed for vinyl, 1,665 sq ft of siding costs $6,700 to $20,000.
What will it cost?
Siding is priced per square foot installed. These two pages turn your area into a price.
How to measure a house for siding
For a simple house, the length of all the walls end to end times the wall height gives the rectangular part. Measure height from where the siding starts to the underside of the eaves. Each gable end adds a triangle: half the gable width times the pitch over 12 is its height, and width times height over 2 its area. A 30 foot gable on a 6:12 roof rises 7.5 feet and adds 112.5 square feet. The roof pitch calculator finds your pitch if you do not know it.
Subtract the windows and doors you will not cover: a 3 by 5 foot window is 15 square feet. Houses with several wall heights, bump-outs or dormers are easiest done wall by wall and added up. If you only know the floor area, HomeGuide’s vinyl siding table works out to siding on roughly 80 to 85 percent of it, about 1,700 square feet on a 2,000 square foot house, but a tape measure beats any ratio. Ply Gem, a siding maker, defines the unit siding is estimated in: one square is 10 by 10 feet, or 100 square feet.
Squares, pieces and boxes
Pieces per square depend on the profile, because a wider face covers more wall. Ply Gem’s examples:
| Profile | Pieces per square | Sq ft per piece |
|---|---|---|
| Double 4 in vinyl (8 in exposure) | 12 | 8.3 |
| Double 4.5 in vinyl | 11 | 9.1 |
| Double 5 in vinyl (10 in exposure) | 10 | 10 |
| 7 in vertical board and batten | 17 | 5.9 |
Ply Gem’s method is the one the calculator uses: total square footage divided by 100 for squares, times the pieces per square for your profile. The square-feet column is our arithmetic. Owens Corning’s Fundamental Series vinyl siding, for one, has an 8 inch exposure and 12 foot 6 inch panels in double 4 inch, a 10 inch exposure and 12 foot panels in double 5 inch, and is packed 2 squares to the carton. Check the carton and the spec guide for the line you buy; insulated and premium lines can be packed differently.
Lap boards: pieces from exposure
For lap boards sold by the piece, such as fiber cement or wood, the coverage of one board is its exposure, the face left showing, times its length. Choose “Lap boards” in the calculator and enter both. For 12 foot boards:
| Exposure | Board length | Covers | Pieces per square |
|---|---|---|---|
| 4 in | 12 ft | 4 sq ft | 25 |
| 5 in | 12 ft | 5 sq ft | 20 |
| 6 in | 12 ft | 6 sq ft | 16.7 |
| 7 in | 12 ft | 7 sq ft | 14.3 |
| 8 in | 12 ft | 8 sq ft | 12.5 |
The exposure is set by the manufacturer for each board width, so take it from the product’s installation instructions rather than measuring the board.
Waste allowance
No source we use publishes a single waste figure for siding. Ply Gem notes that a crew’s efficiency in minimizing scrap can significantly affect material use, along with complex architectural features, window and door openings and the crew’s cutting preferences, and calls its own factors rules of thumb. The calculator starts at 10 percent, the same starting point our roofing square calculator uses for shingles; add more for many gables, dormers and angles, less for long plain walls.
Trim, accessories and nails
Ply Gem estimates accessories from the number of squares. Its factors, in pieces per square, and what they come to for a 20 square house:
| Accessory | Per square | For 20 squares |
|---|---|---|
| Starter strip | 0.8 | 16 |
| J-channel | 2 | 40 |
| Outside corner posts | 0.2 | 4 |
| Utility trim | 0.5 | 10 |
| Inside corner posts | 0.1 | 2 |
| Finish trim, 12 ft | 2 | 40 |
| Soffit channel | 0.8 | 16 |
Many homes need no inside corner posts; Ply Gem suggests two pieces of J-channel can stand in for one. For nails, its general guideline is one third of a pound per square, or, more precisely, square footage times 0.005 for pounds of aluminum nails and times 0.01 for roofing nails, staples or screws. The calculator shows starter strip, J-channel and outside corners, rounded up.
What the siding will cost
Siding is priced per square foot installed, on the area covered rather than the area ordered. HomeGuide puts vinyl at $4 to $12 per square foot installed, and estimates about 1,700 square feet of siding on a 2,000 square foot house. Our vinyl siding cost page prices it by style and house size, and the siding cost calculator covers fiber cement, wood, steel and the other materials.
What this calculator does not do
- Every wall shape. It assumes rectangular walls of one height plus triangular gables; measure dormers and bump-outs separately.
- Soffit and fascia. The eave trim is priced on our soffit and fascia cost page.
- Product-specific packing. Pieces and boxes use the profile and carton size you enter; the label on your product rules.
Sources
- Ply Gem, How to Estimate Accessories for your Siding Job: squares, pieces per square by profile, accessory factors and nail guidelines.
- Owens Corning Fundamental Series Select vinyl siding specification, on Sweets: exposures, panel lengths and 2 squares per carton.
- HomeGuide vinyl siding cost guide, dated January 28, 2025: siding area by house size and installed cost.
- Read on November 5, 2026. Gable areas, lap-board coverage, rounding and the waste default are our own. Every source is listed on the methodology page.
Related calculators and guides
Siding calculator FAQ
How much siding do I need?
Measure the length and height of each wall, add the triangles of the gable ends, subtract windows and doors, and divide by 100 for squares of siding. Then add a waste allowance; the calculator starts at 10 percent. A simple 30 by 50 foot house with 9 foot walls and two 6:12 gables needs about 16.7 squares before waste.
How do you calculate siding for a gable?
A gable is a triangle: its area is the width times the height, divided by 2. The height is half the width times the pitch divided by 12, so a 30 foot gable on a 6:12 roof rises 7.5 feet and has 112.5 square feet of siding.
How many pieces of vinyl siding are in a square?
It depends on the profile. Ply Gem gives 12 pieces per square for double 4 inch, 11 for double 4.5 inch, 10 for double 5 inch and 17 for 7 inch vertical board and batten. Check the spec guide for the product you buy.
How many squares are in a box of vinyl siding?
Usually 2. Owens Corning packs its Fundamental Series vinyl siding at 2 squares, 200 square feet, per carton. Other lines, especially insulated siding, can differ, so check the carton label.
How many boxes of siding do I need for a 2,000 sq ft house?
HomeGuide estimates about 1,700 square feet of siding on a 2,000 square foot house, or 17 squares. With 10 percent waste that is 18.7 squares, or 10 boxes at 2 squares per box. Measure your walls for a real number.
How much J-channel do I need for siding?
Ply Gem's rule of thumb is 2 pieces of J-channel per square of siding, with 0.8 pieces of starter strip, 0.2 outside corner posts and 0.1 inside corner posts. For 25 squares that is 50 pieces of J-channel.
How many nails do I need per square of siding?
About one third of a pound per square, as a general guideline from Ply Gem. For a closer figure it multiplies the square footage by 0.005 for aluminum nails, or by 0.01 for roofing nails, staples or screws, to get pounds.
How much extra siding should I order?
There is no single published figure. Ply Gem notes that openings, complex features and the crew's cutting habits all change how much is used. The calculator starts at 10 percent; add more for many gables, dormers or angles.
What is a square of siding?
A square is 10 by 10 feet, or 100 square feet of wall covered. Siding is estimated and often sold by the square.