Siding Calculator: How to Figure Siding Materials & Cost
Figuring out how much siding you need, and what it will cost, comes down to a few simple measurements and some basic math. Whether you are budgeting for a project or checking a contractor’s quote, this guide walks through it step by step.
In the video above, math and engineering teacher Jonathan Schwartz shows how siding is priced by the board, the linear foot, and the square, using a fiber cement example. This page uses his method, then expands it to a whole house and to installed cost.
How Siding Is Sold
Siding is sold three ways:
By the board: common for fiber cement planks.
By the linear foot: the cost of each foot of board length.
By the square: one square is 100 square feet of wall coverage (10 feet by 10 feet). This is the most useful unit for estimating, and it is how contractors compare products.
Vinyl siding is usually sold in cartons that cover a set number of squares; check the label for the coverage of the product you are pricing.
Step 1: Measure Your Wall Area
For each rectangular wall, multiply its length by its height. Add the walls together for the total.
Schwartz recommends not subtracting windows and doors. The extra area covers waste, cuts, trim work, and fitting adjustments, which keeps you from under-ordering. If you do subtract openings for a tighter number, add about 10 percent back for waste.
Step 2: Add the Gables
Gable ends are triangles. The true area of a triangle is base times height divided by two. For siding, a practical field estimate is base times height times 0.75, which builds in extra material for the waste from angled cuts.
Step 3: Convert to Squares
Divide the total wall area by 100 to get squares, and always round up when ordering.
Worked Example: A Single-Story Ranch
Here is the method on a simple 50-by-30-foot ranch with 9-foot walls and two gable ends that are 30 feet wide and 6 feet tall:
Item | Calculation | Area |
|---|
Walls | Perimeter 160 ft × 9 ft high | 1,440 sq ft |
Gables (2) | 30 ft × 6 ft × 0.75, times 2 | 270 sq ft |
Total | 1,440 + 270 | 1,710 sq ft |
Squares to order | 1,710 ÷ 100, rounded up | 18 squares |
Step 4: Figure the Material Cost
Calculating cost per square is more accurate than per board, because it reflects how much wall each board actually covers. Using Schwartz’s fiber cement example:
Find the reveal. An 8.25-inch board overlaps the one below, so only about 7 inches shows. That visible part is the reveal.
Find each board’s coverage. 7 inches ÷ 12 = 0.58 feet, times a 12-foot board = about 7 square feet per board.
Find boards per square. 100 ÷ 7 = about 14.3 boards.
Find cost per square. 14.3 boards × $13 per board = about $186 per square.
Per linear foot, the same $13, 12-foot board costs about $1.08. On a single wall 8 feet high and 22 feet long (176 square feet, or about 1.8 squares rounded up), material comes to about $335. Board prices vary by region and supplier, so check current local pricing.
Step 5: Estimate the Installed Cost
Material is only part of the bill. Installed prices include labor, tear-off of one existing layer, house wrap, and standard trim. Multiply your wall area by the installed rate for your material:
Material | Installed Cost per Sq Ft | Example Ranch (1,710 sq ft) |
|---|
Vinyl | $4 – $8 | $6,840 – $13,680 |
Engineered wood | $5 – $10 | $8,550 – $17,100 |
Fiber cement | $6 – $13 | $10,260 – $22,230 |
Natural wood | $8 – $15 | $13,680 – $25,650 |
For every material by home size, plus regional pricing and how to compare quotes, see our siding replacement cost guide.
For vinyl specifically, see our vinyl siding cost guide.
Estimating Tips
Always round up when ordering.
Measure every wall, including bump-outs and dormers.
Use the reveal, not the nominal board width, to figure coverage.
Remember trim, corners, J-channel, starter strip, and soffit; they are ordered separately.
Verify current material prices locally before you order.
For the parts that go on the wall besides the siding itself, see our guide to parts of a siding system. If you are deciding whether to do the work yourself, see DIY siding installation vs. hiring a contractor.
Final Thoughts
Measure the walls, add the gables, convert to squares, and multiply by the cost per square or the installed rate. That gives you a solid budget and a way to check any contractor’s quote. For guides on every siding material, visit our siding project hub.
Want a professional measurement and quote? Home Upgrade Pros can connect you with licensed siding contractors for free, no-obligation estimates, or call (725) 745-8553.
Frequently Asked Questions
How do you figure how much siding you need?
Multiply each wall’s length by its height, add the gables (base × height × 0.75), total it up, and divide by 100 to get squares. Round up when ordering.
How many squares of siding for a 2,000-square-foot house?
A typical 2,000-square-foot home has about 1,800 square feet of exterior wall, so roughly 18 squares, plus waste. The real number depends on stories, layout, and gables, so measure your own walls.
What is a square in siding?
100 square feet of wall coverage, a 10-by-10-foot area. It is the standard unit for estimating siding and roofing.
How much does siding cost per square?
It depends on the material. In the fiber cement example above, material alone is about $186 per square. Installed, vinyl runs about $400 to $800 per square and fiber cement about $600 to $1,300.
Why does the siding reveal matter?
The reveal is the part of each board that shows after overlap. It sets how much wall each board covers, which drives the number of boards and the cost.
Should you subtract windows when estimating siding?
Usually not. Leaving them in covers waste and cuts. If you do subtract them, add about 10 percent for waste.
