Deck Joist Calculator
Estimate the number and spacing of deck joists.
How It Works
Joists = ceil((Length × 12) ÷ Spacing) + 1. Total joist length = Joists × Deck width.
Example
A 12 ft deck at 16 in spacing: 10 joists, 10 ft long → 100 linear ft.
Frequently Asked Questions
What joist size should I use?
2×8 or 2×10 are common for residential decks; sizing depends on span and spacing.
Why add one joist?
Like studs, you need a joist at each end of the framing, hence +1.
Does this include rim joists?
No — rim joists and blocking are additional linear footage.