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Deck Board Calculator

Deck Board Calculator

Enter your deck size (square feet or exact dimensions), choose board size, joist spacing and decking angle. Results update in real time — no calculate button needed.

1. Total Square Feet

TOTAL SQUARE FEET:
ft²

If you type here, we’ll use this value and ignore the dimensions below.

OR DIMENSIONS
ft
in
ft
in

2. Board Size

We assume actual face widths of 3.5″ (4‑inch boards) or 5.5″ (6‑inch boards) plus a 1/8″ gap.

3. Joist Spacing

4. Decking Angle

5. Total Length Of Perimeter (optional)

ft

Useful if you plan a picture‑frame border. We’ll add this to the total linear footage required.

Your Decking Materials Calculator Results

BOARD OPTIONS: REQUIRED: WASTE: REQUIRED + WASTE:
Board Screws Required: — Hidden Fasteners Required: —

How the Deck Board Calculator Works

We convert your deck area to the total linear footage of deck boards required, using your selected board face width and a default 1/8″ gap. If you choose 45° decking, we multiply by a diagonal factor (≈1.414) to account for longer runs and offcuts. Finally, we add a standard 5% cut‑waste and show board counts for each common length (8′–20′).

Formulas (simplified)

  • Area (ft²) = given ft², or (Length in ft) × (Width in ft).
  • Effective coverage width (ft) = (board width in″ + 0.125″) ÷ 12.
  • Linear feet required = Area ÷ coverage width × angle factor (1 at 90°, 1.414 at 45°).
  • Boards of length L: ceil( linear feet ÷ L ). Waste adds 5% then rounds up.
  • Fasteners: boards‑across × joists‑along; screws = intersections × 2, hidden clips = intersections × 1.

Fastener estimates need deck length & width. If only area is provided, we approximate using a square deck with side √area.

Frequently Asked Questions

How many deck boards do I need?
Enter your deck size, choose a board width and angle. The calculator converts area to total linear feet and shows counts for 8′–20′ lengths with a default 5% cut-waste.
What are common deck board sizes?
Common faces are ≈3.5″ (2×4 or 5/4×4) and ≈5.5″ (2×6 or 5/4×6). A 1/8″ gap is assumed for coverage.
How do I measure my deck?
Measure length and width to the nearest inch and multiply to get ft². For L-shapes, split into rectangles and add the areas. You can also type total square feet directly.
How does a 45° decking angle affect materials?
Diagonal decking increases total linear footage. We multiply by an angle factor of about 1.414 (√2) compared to 90° runs.
How much waste should I plan for?
We add a standard 5% cut-waste to required boards, then round up to whole boards per chosen length.
How many screws or hidden fasteners will I need?
We estimate fasteners using boards-across × joists-along. Screws = intersections × 2; hidden clips = intersections × 1.
Can I enter total square feet instead of dimensions?
Yes. If you provide ft² we use that directly. For fastener counts without dimensions, we approximate a square deck with side √area.