Lap Siding Calculator
Estimate Siding Material
Enter the dimensions of your wall and siding to calculate the materials needed.
Visualizations
Chart comparing wall area, siding needed before waste, and siding with waste.
| Parameter | Value | Unit |
|---|---|---|
| Total Wall Area | – | sq ft |
| Effective Plank Width | – | inches |
| Number of Rows | – | rows |
| Linear Feet (No Waste) | – | feet |
| Planks (No Waste) | – | planks |
| Linear Feet (With Waste) | – | feet |
| Total Planks Needed | – | planks |
| Estimated Cost | – | $ |
Summary of calculated values for your lap siding project.
Understanding the Lap Siding Calculator
What is a Lap Siding Calculator?
A lap siding calculator is a tool designed to help homeowners, DIY enthusiasts, and contractors estimate the amount of siding material required for a building’s exterior walls. It takes into account the dimensions of the walls, the size of the siding planks, the overlap between planks, and an allowance for waste material generated during cutting and fitting around obstacles like windows and doors. Using a lap siding calculator ensures you purchase enough material without overspending significantly.
This calculator is useful for anyone planning a siding project, whether it’s new construction or re-siding an existing home. It helps in budgeting and planning material orders. Common misconceptions are that you can simply calculate the wall area and buy that much siding; however, the overlap and necessary waste factor mean you need more than the wall’s square footage.
Lap Siding Calculator Formula and Explanation
The lap siding calculator uses the following steps:
- Total Wall Area: Wall Width (ft) × Wall Height (ft) = Total Area (sq ft).
- Effective Plank Width: Siding Plank Width (in) – Overlap (in) = Effective Width (in). This is the exposed width of each plank.
- Number of Rows: (Wall Height (ft) × 12) / Effective Width (in) = Number of Rows (rounded up to the nearest whole number). We convert wall height to inches for this calculation.
- Total Linear Feet (No Waste): Number of Rows × Wall Width (ft).
- Planks Needed (No Waste): Total Linear Feet (No Waste) / Plank Length (ft) (rounded up).
- Total Planks with Waste: Planks Needed (No Waste) × (1 + Waste Percentage / 100) (rounded up).
The core idea is to determine how many rows of siding are needed based on the effective (exposed) width of each plank and then calculate the total length of siding needed for those rows, adding waste.
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Wall Width | Total width of the area to be sided | feet | 10 – 200 |
| Wall Height | Average height of the area to be sided | feet | 8 – 30 |
| Plank Width | Nominal width of one siding plank | inches | 5.25 – 12 |
| Overlap | The amount each plank overlaps the one below | inches | 1 – 1.5 |
| Plank Length | Length of one siding plank | feet | 12 – 16 |
| Waste % | Percentage added for cutting and fitting | % | 5 – 15 |
Practical Examples (Real-World Use Cases)
Let’s see how the lap siding calculator works with some examples.
Example 1: Small Shed
- Wall Width: 10 feet
- Wall Height: 8 feet
- Plank Width: 6.25 inches
- Overlap: 1.25 inches
- Plank Length: 12 feet
- Waste: 8%
Total Area: 80 sq ft. Effective width: 5 inches. Rows: (8*12)/5 = 19.2 -> 20 rows. Linear feet (no waste): 20 * 10 = 200 ft. Planks (no waste): 200/12 = 16.67 -> 17 planks. Total planks (with waste): 17 * 1.08 = 18.36 -> 19 planks.
Example 2: House Wall Section
- Wall Width: 50 feet
- Wall Height: 9 feet
- Plank Width: 8.25 inches
- Overlap: 1.25 inches
- Plank Length: 12 feet
- Waste: 12%
Total Area: 450 sq ft. Effective width: 7 inches. Rows: (9*12)/7 = 15.43 -> 16 rows. Linear feet (no waste): 16 * 50 = 800 ft. Planks (no waste): 800/12 = 66.67 -> 67 planks. Total planks (with waste): 67 * 1.12 = 75.04 -> 76 planks.
Using the lap siding calculator for these scenarios helps in accurately ordering materials.
How to Use This Lap Siding Calculator
- Enter Wall Dimensions: Input the total width and average height of the walls you plan to side in feet.
- Specify Siding Details: Enter the nominal width of the siding planks and the desired overlap in inches. Also, input the length of the planks in feet.
- Estimate Waste: Add a waste percentage. This accounts for material lost during cutting, especially around windows, doors, and gables. 10-15% is common for complex walls, 5-10% for simpler ones.
- Add Cost (Optional): If you know the cost per plank, enter it to get an estimated material cost.
- Calculate: The calculator will automatically update the results as you input values.
- Review Results: The primary result is the “Total Planks Needed (with waste)”. Intermediate values like total area, rows, and linear feet are also shown.
The results from the lap siding calculator guide your material purchase. Always round up the number of planks to ensure you have enough.
Key Factors That Affect Lap Siding Calculator Results
- Wall Complexity: Walls with many windows, doors, gables, or angles require more cuts, increasing the waste percentage. A simple rectangular wall needs less waste allowance.
- Overlap Amount: A larger overlap means less exposed siding per plank, increasing the total number of planks needed. Standard overlaps are often 1″ to 1.5″.
- Plank Width and Length: Wider planks cover more area per row, but the effective width after overlap is key. Longer planks might reduce the number of butt joints but can be harder to handle and may lead to different waste patterns.
- Starter Strips and Trim: This lap siding calculator focuses on the field siding. Remember to account for starter strips, corner trim, J-channels (for vinyl), and other trim pieces separately.
- Material Type: While the calculation is geometric, the material (vinyl, fiber cement, wood) can influence waste due to breakage or cutting characteristics.
- Installer Skill: An experienced installer might minimize waste more effectively than a novice DIYer. It’s wise for beginners to add a slightly higher waste percentage.
Consider these factors when using the lap siding calculator and planning your project.
Frequently Asked Questions (FAQ)
- 1. How much extra siding should I buy for waste?
- Typically, 5-10% for simple walls and 10-15% for complex walls with many cuts. Our lap siding calculator includes a field for this.
- 2. Does this calculator work for all types of lap siding?
- Yes, it works for vinyl, fiber cement (like HardiePlank), wood, and engineered wood lap siding, as long as you know the plank dimensions and overlap.
- 3. What if my walls are different heights?
- Use the average height, or calculate each wall section separately and add the results if heights vary significantly.
- 4. How do I calculate siding for gables?
- Gables (triangular wall sections) generate more waste. Calculate the gable area (0.5 * base * height) and treat it as a rectangular area with a higher waste factor (e.g., 15-20%) when using the lap siding calculator principle, or calculate separately.
- 5. Does the calculator account for windows and doors?
- The waste percentage is intended to cover cuts around windows and doors. For very large openings, you could subtract their area from the total wall area, but increasing waste is often simpler and safer.
- 6. What is “effective width” or “exposure”?
- It’s the part of the siding plank that is visible after installation, i.e., nominal width minus the overlap.
- 7. Should I round up the number of planks?
- Yes, always round up to the nearest whole number of planks to ensure you have enough material.
- 8. Does the cost include installation?
- No, the optional cost calculation is for materials (planks) only. See our hiring a siding contractor guide for labor cost info.