How Much Siding Do I Need? Measuring in Squares

What a "square" of siding is

Siding is sold and quoted by the square: 100 square feet of wall coverage. A house with 2,000 square feet of wall area needs about 20 squares of siding before waste. Quotes often list squares for siding and linear feet for trim, corners, soffit and fascia.

Wall area is not the same as the home's living area. A 1,500-square-foot ranch might have roughly 1,200 to 1,800 square feet of wall area depending on its shape, wall height and gables; a two-story house of the same floor area has much more wall per square foot of floor.

Step 1: Measure the rectangular walls

For each wall, measure the length along the foundation and the height from the bottom of the siding to the soffit (or to where the gable starts). Multiply length by height. A tape measure and a helper work; a laser measure makes heights easier. Do not climb onto the roof to measure.

• Break L-shaped and bumped-out walls into simple rectangles.
• For a two-story wall, measure the height in two parts if a ladder is needed, or estimate from courses: count the rows of siding and multiply by the exposure (for example, 4 or 5 inches per row).

Step 2: Add the gables

A gable (the triangle under a roof peak) has an area of one half times the base times the height. Measure the base (usually the width of that wall) and estimate the height from the top of the wall to the peak. Counting siding courses from the ground works here too.

Step 3: Subtract large openings

Subtract garage doors, large picture windows, patio doors and areas of stone or brick that will not be sided. Many estimators do not subtract ordinary windows and entry doors, because the extra material covers waste around them; others subtract them and add more for waste. Either approach works if you are consistent.

Step 4: Add waste

Cutting around windows, gables and corners creates scrap. Around 10% is a common allowance for simple houses; houses with lots of gables, angles and dormers may need more. Contractors add waste based on the product and the house.

Step 5: Divide by 100

Total wall area plus waste, divided by 100, equals squares of siding.

Worked example: a Wichita-area ranch

Here is an illustration with round numbers (an example of the math, not a measurement of any real house):

Most contractors would round up to 19 squares for ordering.

Don't forget trim, soffit and fascia

• Outside and inside corners: count corners and multiply by wall height.
• Starter strip: the length of the bottom of every wall.
• J-channel or window trim: the perimeter of each window and door, plus gable edges.
• Soffit: the length of the eaves times the overhang depth; quotes often use linear feet.
• Fascia: the length of the roof edges where gutters or trim run.
• House wrap: roughly the wall area, sold in rolls.

Using your estimate to check quotes

When quotes arrive, compare the squares each contractor lists with your own estimate. If one is far higher, ask why (more waste, more gables than you counted, different exposure). If one is far lower, ask what is missing. Differences of a square or two are normal. HomeGuide's published guide lists typical installed costs per square foot by material, and the siding cost guide collects more ranges, so you can multiply your area by a range to get a rough budget. Real prices depend on the product, the house and the contractor.

Why contractors measure for themselves

Contractors measure every wall, often with aerial measurement reports or laser tools, because ordering too little delays the job and different products have different coverage per carton. Their number is the one that goes on the order; yours is for planning and comparison.

Common measuring mistakes

• Forgetting gables, dormers and the walls of attached garages.
• Measuring to the roof line instead of the soffit, or missing walls above lower roofs.
• Subtracting every window and then not adding enough waste.
• Leaving out areas behind decks, porches or large shrubs.
• Ignoring soffit, fascia and trim, which can be a large share of the job on a house with deep eaves.

Buying extra for repairs

Ask for a few spare panels or boards of each profile and color to keep in the garage. Siding lines and colors change, and having matching pieces on hand makes future repairs after a storm much easier.

Related services

• Siding Replacement: Tear off worn or damaged siding and re-side the house in vinyl, fiber cement, engineered wood or steel.
• Siding Installation: New siding for additions, new builds, garages and shops, installed to the manufacturer's instructions.
• Vinyl Siding: Low-maintenance vinyl in standard and insulated grades, chosen for Kansas wind and hail.

Sources: HomeGuide, house siding cost.

Good to know: Requesting a quote is free and there is no obligation. Ask for a written quote that lists the material, the scope, permits and the warranty terms.