Siding Calculator

The Siding Calculator estimates how much siding you need in squares — the trade unit where 1 square = 100 square feet of coverage. It multiplies your wall perimeter by height, adds any triangular gable ends, subtracts windows and doors, applies a waste factor tuned to your siding type, and converts the result into squares, boxes to order, and an estimated material cost — with an animated house elevation and a visual squares breakdown so the numbers are easy to picture.

What is a "Square" of Siding?

Siding, like roofing, is sold and priced by the square. One square covers 100 square feet of finished wall. So a home with 1,500 square feet of net wall area needs 15 squares of siding before waste. Working in squares makes it easy to compare quotes and order the right number of boxes, because manufacturers list coverage per carton in squares too.

Siding Formula

The calculation is a short chain: gross wall area, minus openings, plus waste, divided by 100.

How Much Waste Should You Add?

Waste covers cut-offs, corners, mistakes, and pattern matching. Use this as a guide, then round up to whole boxes:

Siding Types & Coverage

Coverage per box varies by brand and exposure, so always check the product label — this calculator lets you override the default coverage to match your exact product.

What Affects Your Siding Estimate?

How to Use This Calculator

1. Enter wall dimensions: Pick Feet or Meters, then enter the total wall perimeter around your home and the wall height.
2. Add gables and openings: Enter the number of gable ends with their base and rise, plus how many doors and windows to subtract and any extra opening area.
3. Choose siding type and waste: Selecting a siding type auto-fills an informed waste factor and coverage per box, which you can adjust.
4. Calculate: See the squares of siding needed, boxes to order, estimated cost, an elevation diagram, a squares grid, and a full step-by-step breakdown.

Frequently Asked Questions

What is a square of siding?

A square is the standard unit siding is sold and priced in. One square equals 100 square feet of finished wall coverage. If your net wall area is 1,500 square feet, that is 15 squares of siding before waste.

How do I calculate how much siding I need?

Multiply your wall perimeter by the wall height to get the gross wall area, add any triangular gable areas, subtract the area of windows and doors, add a waste factor of about 10 to 15 percent, then divide by 100 to convert to squares.

How much waste should I add for siding?

A waste factor of 10 percent is typical for simple rectangular homes with vinyl or aluminum siding. Add 12 to 15 percent for fiber cement, wood, board and batten, or shakes, and for homes with many corners, gables, or angled cuts.

Do I subtract windows and doors from siding?

Yes. Subtract the area of large openings such as windows and doors from the gross wall area. This calculator uses about 21 square feet per door and 12 square feet per window by default, and you can add any additional opening area.

How do I include gable ends?

A gable is the triangular section of wall beneath a pitched roof. Its area is one half times the base width times the vertical rise. Enter the number of gables plus the base and rise, and the calculator adds that triangular area to your walls.

How many boxes of siding do I need?

Divide your total wall area including waste by the coverage per box, then round up. Vinyl and aluminum cartons typically cover about 200 square feet (2 squares), while fiber cement, engineered wood, and wood lap boxes usually cover about 100 square feet.

Additional Resources

• Siding - Wikipedia
• Gable - Wikipedia