Fibre-cement, engineered-wood and wood clapboard siding are installed as overlapping planks; only the exposure (the part not covered by the next course) counts toward coverage. A 8¼ in fibre-cement plank typically has a 7 in exposure. Siding is also quoted by the square (100 ft²).
How to use the Siding Calculator
- House perimeter
- Wall height
- Gable ends
- Gable width
- Gable height
- Doors and windows area
- Plank exposure
- Plank length
- Waste
- Price per plank
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the perimeter of the house, wall height, gables, openings, plank exposure and length, waste and price per plank.
Tips for an accurate estimate
- Take measurements at floor level and at the ceiling – walls and rooms are often slightly out of square.
- Use the manufacturer’s coverage, spacing and installation data when it differs from the typical values here.
- Keep a little extra of every finish material for touch-ups and repairs later.
- Check local building codes and permits before structural, electrical, plumbing or gas work.
Common mistakes to avoid
- Sizing heating or cooling equipment by area alone when insulation, windows and climate make a big difference.
- Buying too little paint, stain or flooring and ending up with mismatched batches.
- Overlooking the extra material for steps, railings, gables and trim.
Inputs explained
| Field | What to enter |
|---|---|
| House perimeter | Units: ft, m, in, yd, cm |
| Wall height | Units: ft, m, in, yd, cm |
| Gable ends | A number |
| Gable width | Units: ft, m, in, yd, cm |
| Gable height | Units: ft, m, in, yd, cm |
| Doors and windows area | Units: ft², m², yd², acre |
| Plank exposure | Units: in, cm, mm, ft, m |
| Plank length | Choose one: 12 ft, 16 ft, 3.66 m, 4.88 m |
| Waste | In % |
| Price per plank | Units: /piece |
What each result means
- Net siding area = max([House perimeter]×[Wall height] + [Gable ends]×[Gable width]×[Gable height]÷2 – [Doors and windows area], 0)
- Squares (100 ft²) = [Net siding area]÷9.290304
- Planks = ceil([Net siding area]÷([Plank exposure]×[Plank length])×(1 + [Waste]÷100))
- Cost = [Planks]×[Price per plank]
Example values
How the main result changes when House perimeter changes and everything else stays at the example values above:
| House perimeter (ft) | Planks |
|---|---|
| 80 | 117 |
| 120 | 173 |
| 160 | 230 |
| 200 | 286 |
| 240 | 343 |
| 320 | 456 |
Formula
Net area = perimeter × height + gables × width × height ÷ 2 − openingsPlanks = ceil(net area ÷ (exposure × plank length) × (1 + waste))Worked example
Inputs — House perimeter: 160 ft; Wall height: 9 ft; Gable ends: 2; Gable width: 30 ft; Gable height: 8 ft; Doors and windows area: 220 ft²; Plank exposure: 7 in; Plank length: 12 ft; Waste: 10 %; Price per plank: $14 /piece.
Results — Net siding area = 1,460 ft²; Squares (100 ft²) = 14.6; Planks = 230; Cost = $3,220.00.
Frequently asked questions
How many siding planks per square?
With a 7 in exposure and 12 ft planks, about 14.3 planks per 100 ft².
How much waste for siding?
10% for simple walls, 15% with many gables, dormers or openings.
Do I subtract windows from siding area?
Yes for large openings; trim boards around them are bought separately.
What formula does the Siding Calculator use?
Net area = perimeter × height + gables × width × height ÷ 2 − openings.