Vinyl Siding Calculator

Work out the total wall area, subtract the openings, then add a waste allowance. Measure each wall’s length times its height and add them up, add the triangular gable areas (half the base times the height), then subtract the area of windows, doors and garage doors. That gives the net area to cover.

Add a waste allowance — about 10 percent for a simple house, more for complex shapes — then convert to squares by dividing by 100, since siding is sold by the square (100 square feet).

Example: a 40 by 30 foot house with 9-foot walls has about 1,260 square feet of wall; after subtracting openings and adding 10 percent waste you might order around 13 to 14 squares, or 7 boxes of two squares each.

A square is the standard unit for siding and roofing: 100 square feet of coverage. It is how siding is priced and ordered, rather than by the individual panel.

Vinyl siding is usually boxed two squares to a carton, so one box covers about 200 square feet. If your house needs 13 squares of coverage, that is about 7 boxes once you round up to whole boxes.

Thinking in squares makes it easy to compare prices and quantities, because a price per square is directly comparable across brands and profiles even when the panel sizes differ.

Add about 10 percent for a simple, boxy house, 15 percent for a home with several gables, corners and openings, and up to 20 percent for a complex design with lots of cuts, angles and architectural detail.

Waste covers the offcuts left when panels are trimmed to length, the overlap at panel ends, and the occasional mistake or damaged piece. Steeper gables and many windows create more cuts and more waste.

It is better to order a little extra than to run short, since dye lots vary between production runs and a later box may not match the color of the siding already installed. Keep a few leftover pieces for future repairs.

Divide your order area (net area plus waste) by 100 to get squares, then divide by 2 and round up, since a box holds two squares (about 200 square feet).

For example, 1,300 square feet of order area is 13 squares, which is 6.5 boxes, so you would buy 7 boxes. Always round up to whole boxes because suppliers sell full cartons, not partial ones.

Buy all the siding for a job at once and check that the boxes share the same dye lot or production run, so the color is consistent across the whole house.

Besides the siding panels, a typical job needs starter strip along the bottom of each wall, J-channel around windows, doors and along the roof line, outside and inside corner posts at the corners, and finish or utility trim under the eaves and window sills.

You will also need siding nails — roughly a pound per square — plus any under-sill trim, light blocks and dryer or vent blocks for penetrations. These accessories are what make the installation weather-tight and give it a finished look.

The amounts depend on the house shape: more corners mean more corner posts, and more windows mean more J-channel, so the trim list grows with the number of openings and breaks in the walls.

You can, and this calculator does by default, but many installers leave small windows in the total as extra insurance against running short. Large openings like garage doors, big picture windows and sliding doors are always worth subtracting because they remove a meaningful amount of area.

The trade-off is simple: subtracting openings gives a tighter, more accurate material figure, while not subtracting them builds in a safety margin similar to extra waste. On a house with many windows the difference can be a box or two of siding.

A common approach is to subtract only the large openings and keep the small ones in, then rely on the waste percentage to cover cuts around every opening.

A gable is the triangle of wall between the eave line and the roof peak. Its area is half the base times the height — the base is the width of the wall, and the height is the vertical rise from the eave line up to the peak.

For a 30-foot-wide gable that rises 8 feet to the peak, the area is 0.5 times 30 times 8, or 120 square feet. Count one gable for each triangular end you are siding; a simple gable roof has two, while a hip roof has none.

If you do not know the rise, you can estimate it from the roof pitch, but measuring the actual peak height from the eave line is more accurate for ordering material.

Materials for vinyl siding commonly run from a little over one dollar to a few dollars per square foot, or roughly $130 to $250 per square depending on the profile and grade. Installed, a typical vinyl siding job often lands somewhere around $4 to $12 per square foot including labor.

Standard profiles like double 4-inch lap are the most economical, while premium looks such as board and batten or insulated siding cost more. Labor, trim, house wrap and removal of old siding all add to the total.

For a closer figure, enter your house size, profile and local prices, and remember this covers siding and basic trim only — soffit, fascia, house wrap and old-siding removal are usually priced separately.