Understanding Siding Calculation
Siding is typically sold by the square (100 sq ft) or by the box. The most accurate way to calculate material is based on the **panel coverage area**. This area is determined by the panel's **installed length** and its **exposure width** (the part that remains visible after overlapping the course below).
Key Terms and Formula
- **Exposure Width:** The vertical distance (in inches) that one course of siding covers when installed, not the full height of the panel.
- **Panel Coverage Area:** Calculated as $\text{Panel Length (ft)} \times (\text{Exposure Width (in)} / 12)$.
- **Waste Allowance:** An essential factor (typically 5%–15%) to account for cutting around windows, doors, and gables, as well as starter and termination pieces.
- **Formula for Panels:** $\text{Total Panels} = \text{Wall Area (sq ft)} \times (1 + \text{Waste \%}) / \text{Coverage Sq Ft per Panel}$
Important: Trim and Accessories
This calculator **only** estimates the main siding panels. You must separately calculate and purchase trim pieces like $\mathbf{J\text{-}Channel}$, $\mathbf{F\text{-}Channel}$ (for soffit), inside/outside corners, starter strips, and mounting blocks for lights and vents.