Siding Materials Calculator
The Siding Materials calculator shows the panel or square count you’ll need—plus trim lengths—after subtracting windows and doors and applying a realistic waste factor.
We let you enter either a known wall area or a building’s total wall length and average height to estimate coverage. Add total openings area, choose your panel size (e.g., 4×8), and set waste. We’ll compute panels, squares, and trim lengths for corners and openings so you can plan purchases or verify quotes. If you prefer manual math, the formulas and steps are below.
Enter a known wall area or use total wall length × average height. Subtract the total openings area, set a waste %, and pick a panel size. Optional: add outside corner count and opening size/count to estimate trim lengths.
Choose how we compute gross wall area before subtracting openings.
Sum of windows, doors, garage doors, etc.
Common sheets: 4×8, 4×9, 4×10.
Typical 8–15%, more for complex elevations.
We’ll multiply by wall height for LF.
Used to estimate perimeter trim (J-channel/casings).
These are planning estimates. Confirm manufacturer coverage, trim profiles, and local code before ordering.
Results interpretation
How it works
We compute gross wall area, subtract openings, apply waste, and divide by panel coverage.
Formulas, assumptions, limitations
Gross area. Either your known ft² or (total wall length × average height).
Openings. Subtract total openings area (windows/doors/garage doors) from gross area.
Waste. Apply a percentage to account for cuts, layout, patterns, and material defects.
Panels. Panels = ceil( NetWithWaste ÷ (PanelWidth × PanelHeight) ).
Squares. Squares = NetWithWaste ÷ 100.
Trim. Outside corners = count × height. Openings trim = count × 2 × (avg width + avg height).
Use cases & examples
Gross 1800 ft² → net 1680 ft² → with waste 1848 ft². Panels = ceil(1848/32) = 58. Squares ≈ 18.48. If 8 outside corners: 8×10 = 80 LF. Ten 3×4 ft openings → 10×2×(3+4)=140 LF trim.
Net 2000 ft² → with waste 2240 ft². Panels = ceil(2240/36) = 63. Squares ≈ 22.40. Corners/trim as entered.
Gross 504 ft² → net 464 ft² → with waste 501 ft². Panels = ceil(501/32) = 16. Squares ≈ 5.01. If 4 corners: 4×9 = 36 LF.
Siding calculator FAQs
What is a square in siding?
A square is 100 square feet of siding coverage.
How should we choose waste %?
Simpler elevations may use ~8–10%; complex facades, patterns, and many openings can push 12–15% or more.
Do panel seams and orientation matter?
Yes for layout and waste, but for a quick takeoff, area coverage is a reliable baseline. Confirm final layout before ordering.
How accurate are trim estimates?
They’re planning numbers based on counts and typical sizes. Verify specific profiles (J-channel, corners, starters) and add spares.
Can we use lap siding instead of panels?
This tool approximates by area. For lap products, coverage per course and exposure change the counts—use manufacturer tables to refine.
What about sheathing wrap and flashing?
Include house wrap, flashing, and sealants per code and manufacturer instructions.
Plan siding like a pro: from wall area to an order list
Successful siding projects start with a clean quantity takeoff. We translate your dimensions into coverage, add a practical allowance for waste, and convert results into panels (or squares) and trim lengths. That turns a fuzzy scope into a punchy materials list you can compare across suppliers and installers.
1) Measure wall area
The fastest path is total wall length × average height for each elevation, summed around the building. If your site has gables, dormers, or bump-outs, fold those into the average or add them separately. If you already have a wall area from plans or scans, use it directly.
2) Subtract openings
Remove the area of windows, doors, large sliders, and garage doors. For a quick estimate, it’s fine to use a single total number. Precision improves if you list each opening, but it’s not required for a solid baseline.
3) Apply a realistic waste factor
Waste covers layout cuts, course alignment, pattern matching, and on-site issues. Simpler rectangles often land near 8–10%; complex façades and mixed cladding can require 12–15%+. Order a little extra to avoid color-lot mismatches if you run short mid-project.
4) Convert coverage to panels and squares
Panels are sold by size (e.g., 4×8, 4×9, 4×10). We divide coverage by panel area and round up. We also express the same coverage in squares (100 ft²) so quotes using roofing-style units line up cleanly.
5) Don’t forget trim
Outside corner trims run the full height of each corner. Around openings, expect perimeter trim like J-channel or casings. Our estimate multiplies counts by typical perimeters, but verify your profile lengths and accessories: starter strips, Z-flashings, belly bands, and specialty trims.
Field tips for smoother installs
- Confirm substrate flatness and flashing details before cladding begins.
- Store panels flat and protected from moisture; acclimate per manufacturer guidance.
- Prime and seal cut edges where required to preserve warranties.
- Use corrosion-resistant fasteners; check shank type and spacing.
- Mind expansion gaps and caulk where specified—movement matters.
Quality checks
Before signing off, verify course alignment, consistent reveals, proper joint staggering, clean cuts at openings, and intact weather-resistive barriers. Photograph in-progress work for documentation.
Budgeting and contingency
Material overage is cheaper than a mid-job delay. If you’re ordering color-sensitive products, one extra panel bundle can save a world of pain later. Keep trim spares for future repairs.
From estimate to purchase
With coverage, panel counts, and trim lengths in hand, request written quotes that include lead times and delivery options. Ask suppliers to confirm coverage per unit on the exact SKUs you plan to install.