🪵Deck Calculator
Work out deck boards, joists, beams, posts, screws and footing concrete for your new deck.
Your deck
You'll need about
29 deck boards
192 sq ft · 26 rows of 1 (incl. 10% waste)
sq ft
192
joists
13
posts
9
80 lb bags
45
beams
3
screws
676
🛒 Shopping list
- Deck boards (16 ft)29 boards
- Joists (2×8, 12 ft)13 joists
- Beam boards (2×10, doubled)12 boards
- Posts (6×6)9 posts
- Concrete for footings (80 lb)45 bags
- Deck screws (box of 350)2 boxes
Boards run the long way, joists run across. Check your local code for footing depth — it depends on your frost line.
How it works
Boards run the length of the deck. Rows = deck width ÷ (board width + ⅛–³⁄₁₆ in gap), and each row needs deck length ÷ board length boards. Joists run across the deck at your chosen spacing: joists = length ÷ spacing + 1. Beams sit about every 8 ft, with posts every 8 ft along each beam and about five 80 lb bags of concrete per footing.
Worked example
A 16 × 12 ft deck with 5.5 in boards, 16 ft long, joists 16 in apart:
- 12 ft × 12 ÷ 5.69 in = 26 rows of 1 board → 29 boards with 10% waste
- 16 ft × 12 ÷ 16 + 1 = 13 joists
- 3 beam lines × 3 posts = 9 posts and 45 bags of concrete
- 26 rows × 13 joists × 2 = 676 screws → 2 boxes
Questions people ask
16 in is standard for wood decking. Many composite boards need 12 in, especially laid on a diagonal. Check your board's instructions.
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Last updated September 28, 2026. These results are friendly estimates to help you plan — always double-check before buying or making big decisions.