Siding calculator for walls, gables and board and batten
This siding calculator works out how much siding a house, shed or garage needs. Enter the total wall length and height, the gable ends and the windows and doors, and it gives the net area, the number of siding squares, and how many pieces to buy for lap siding, or how many boards and battens for board and batten.
It is a siding calculator for square feet and for gable ends: each gable is a triangle of ½ × width × rise, and the openings are taken off. A second mode is a board and batten calculator that counts boards and battens from the batten spacing, in feet and inches or in metres and millimetres, so it works as a metric board and batten calculator too.
The calculation runs in your browser and rounds up. Follow the product's installation guide for exposure, nailing, trim and flashing, and ask your supplier about lengths.
How to use the Siding & Board-and-Batten Calculator
- Choose lap or panel siding, or board and batten, and your units.
- Enter the total length of the walls to clad and the wall height.
- Add the gable ends with their width and rise, then the windows and doors with their areas.
- Set the waste allowance, the exposure (lap) or board width (board and batten) and the piece length.
- Read the squares and pieces, or the boards and battens, and copy the summary.
Siding & Board-and-Batten Calculator features
Walls plus gables
Rectangles for the walls and triangles for gable ends, with openings deducted.
Squares and pieces
Squares of 100 ft² (9.29 m²) and the count of siding pieces from their exposure and length.
Board and batten
Boards and battens counted from the batten spacing and stock length.
Imperial or metric
Feet and inches, or metres and millimetres, with 8 to 16 ft and 2.4 to 4.8 m lengths.
Interior walls too
Treat one wall as the perimeter to plan board-and-batten panelling.
How to calculate siding
Net area = wall length × height + gable areas − windows and doors. In the default example the walls are 120 ft × 9 ft = 1,080 ft². Two gables 30 ft wide and 8 ft high add 2 × ½ × 30 × 8 = 240 ft², making 1,320 ft². Eight windows of 15 ft² and two doors of 21 ft² come off, leaving 1,158 ft².
Add waste, 10% here, to get 1,273.8 ft², or 12.7 squares (one square is 100 ft²). A 6 in exposure on 12 ft pieces covers 0.5 × 12 = 6 ft² each, so 1,273.8 ÷ 6 = 212.3, which rounds up to 213 pieces.
For board and batten, a board runs the full height and a batten covers each joint, so the number of runs is the wall length divided by the board width. The calculator uses the net area divided by the spacing to get the total length of boards (and of battens), then divides by the stock length: with 12 in spacing that is 1,273.8 ft ÷ 12 ft = 106.2, so 107 boards and 107 battens. This area method follows the gable taper but cannot show how pieces are cut from stock lengths, so keep the waste at 10 to 15%.
Common sizes
Sizes vary by maker, so these are starting values to edit.
| Item | Typical value | Note |
|---|---|---|
| Lap siding exposure | 4 to 8 in (100 to 200 mm) | Set by the product; 6 in is common |
| Piece length | 12 ft (3.66 m) vinyl panels | Fibre-cement and wood come in 8 to 16 ft |
| Board width | 10 to 12 in (250 to 300 mm) | A 1×12 board is about 11¼ in wide |
| Batten width | 1½ to 2½ in (40 to 60 mm) | Covers the joint between boards |
Limits and tips
- Trim, J-channel, corner posts, soffit, fascia, house wrap, nails and flashing are separate items and are not included.
- Complex shapes with many dormers or bays need more waste. Measure large features separately and add them as extra walls.
- To frame the wall behind the siding use the stud calculator; for the interior finish the drywall calculator; to paint it afterwards the paint calculator; and for the roof the roofing calculator.
Siding & Board-and-Batten Calculator FAQ
How do I calculate siding square footage?
Multiply the total wall length by the height, add the gable areas (½ × width × rise each), then subtract windows and doors. Add 10% for waste. The result in square feet divided by 100 is the number of siding squares.
How much siding do I need for gable ends?
Each gable is a triangle: ½ × the width at the base × the rise. A 30 ft wide gable with an 8 ft rise is 120 ft². Enter the number of gables, their width and rise.
How many board and batten pieces do I need?
Divide the net area by the board width (batten spacing) to get the total length of boards, then divide by the stock length. For 1,274 ft² at 12 in spacing with 12 ft boards that is 107 boards and 107 battens.
How do I use a board and batten calculator for a whole room?
Treat each wall you will panel as the wall length, leave the gables at 0, subtract the doors and windows, and set the batten spacing. Add up the rooms by adding the wall lengths.
Does the siding calculator work in metric?
Yes. Switch to metres and millimetres, and choose a piece length such as 3.6 m. Squares are still shown as 100 ft² (9.29 m²) for comparing with US products.
How much extra siding should I buy?
About 10% for simple walls and 15% where there are many cuts, angles or gables. Buy all the siding from one lot so the colour matches.