Home & Cooking
Deck Calculator
Estimate deck boards, joists, beams, posts, concrete, screws, and railing for a wood deck. Supports 12, 16, or 24 in joist spacing and optional pricing.
Deck details
Railing
Optional pricing (USD)
Leave any field blank to skip the cost line.
Materials you need
26 boards, 13 joists
- Deck area
- 192 sq ft
- Joist linear feet
- 156 ft
- Beams
- 2 (32 ft)
- Posts
- 6
- Concrete bags (one per post)
- 6
- Deck screws
- 5.8 lb
- Railing linear feet
- 40 ft
- Railing posts
- 8
Frequently Asked Questions about the Deck Calculator
How many deck boards do I need?
Divide deck width by board width plus gap to get the number of rows, then multiply by stock boards per row (deck length divided by stock board length, rounded up). A 16 by 12 ft deck with 5.5 in boards and 12 ft stock needs about 52 boards.
What joist spacing should I use for a deck?
16 in on center is standard for 5/4 in or 1 in thick boards. Drop to 12 in on center for diagonal patterns or thinner composite decking. 24 in spacing only works with 2 in thick boards rated for that span.
How many posts and concrete bags do I need?
Most decks use two parallel beams. Each beam needs one post at each end plus an extra one for every 8 ft of length. A 16 ft beam takes 3 posts; a 16 by 12 deck takes 6 posts. Plan one 50 lb bag of concrete per post.
How much railing material do I need?
Take the deck perimeter and subtract the side that sits against the house. A 16 by 12 deck attached on one long side has 56 ft of perimeter minus 16 ft, so 40 ft of railing. Railing posts go at no more than 6 ft on center.
How many deck screws should I buy?
A common rule is 3 lb of #8 by 2.5 in deck screws per 100 sq ft. A 192 sq ft deck needs about 5.8 lb of screws, roughly one 5 lb box plus a small extra pack.