Wall Area Calculator
The rectangular wall area of a house: perimeter times wall height. Add the gables separately and subtract the openings to get the net area to side.
A 140 ft perimeter with 10 ft walls is about 1,400 sq ft of rectangular wall (perimeter × height), before the gable triangles and before you subtract openings. Add the gables separately and deduct the doors, windows and garage for the net siding area.
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The rectangular walls are the bulk of any siding job, and their area is the simplest identity in the whole estimate: perimeter times height. Everything else — gables, dormers, openings, waste — is an adjustment on top of this base rectangle.
Use this tool when you want the wall area on its own: to sanity-check a contractor’s take-off, to price a single elevation, or as step one before you add gables and subtract openings. It treats the house as a band of wall wrapped around the footprint — which is exactly what lap siding is.
Perimeter × height, and why it works
Unroll the four (or more) walls into one long strip and the area is length × height. The length is the perimeter; the height is the wall height. Corners do not change the total area — they only change where the cuts fall, which is what the waste factor covers later. If different walls have different heights, run each wall as its own perimeter × height and add the results.
Formula
wall_area = perimeter × wall_height
For walls of unequal height: wall_area = Σ (wall_length × that_wall_height). This tool assumes one common height; split the job by elevation if your walls differ.
Worked example
A house with a 140 ft perimeter and 10 ft walls:
140 × 10 = 1,400 sq ft of rectangular wall.
This is before the gable triangles are added and before the doors, windows and garage are subtracted. On the sample house those adjustments take it to 1,336 sq ft net.
Getting the two numbers right
- Perimeter is the walk-around distance at the base of the walls — include every jog, bump-out and return, or the strip comes up short.
- Height stops at the soffit. The triangle above the eaves is a gable, handled by the gable area calculator.
- Uneven grade? Walls can be taller on the downhill side. Measure each side and add per-wall areas rather than using one height.
- This is gross wall. Subtract the openings for the net area you actually side.
Reference table
Labeled planning typicals — measure your actual openings. Subtract these from the gross wall + gable area.
| Opening | Deduct (sq ft) |
|---|---|
| Standard door (3 × 7) | 21 |
| Standard window | 15 |
| Patio / sliding-glass door | 40 |
| Single garage door (9 × 7) | 63 |
| Double garage door (16 × 7) | 112 |