Deck Calculator
Estimate decking boards (lineal feet and count), joists at your chosen spacing, and screws for a deck.
Processed locally in your browser — nothing is uploaded.
Deck Calculator
Direction the deck boards run
5.5 in = actual width of a "6-inch" board
Enter the deck dimensions to estimate materials.
About Deck Calculator
Enter the deck size, board width and gap (5.5 in — the actual width of a nominal 6 in board — and 1/4 in gap by default), and a joist spacing of 12, 16, or 24 in on center. It returns board rows, lineal footage with waste, a board count at your stock length, the joist count, and screws at roughly 350 per 100 sq ft.
Common uses
- Order decking and fasteners for a 16×12 deck
- See how 24 in joist spacing changes the lumber count
Example
Input
16 × 12 ft deck, 5.5 in boards + 1/4 in gap, 16 in OC, 10% waste
Output
26 rows · 458 lineal ft → 29 16-ft boards · 13 joists · ~672 screws
Limitations
- Covers decking and joists only — beams, posts, footings, and stairs are separate
- Assumes boards run the full deck length with butt joints landing on joists
Frequently asked questions
How many deck boards do I need for a 16x12 deck?
With 5.5 in boards and a 1/4 in gap, a 16×12 ft deck takes 26 rows of decking — 416 lineal feet, or about 458 with 10% waste. That's 29 boards in 16 ft stock lengths.
How many screws do I need per square foot of decking?
About 3.5 — two screws at every joist crossing works out to roughly 350 screws per 100 sq ft with 16 in joist spacing, which is the rate this calculator uses.
What gap should I leave between deck boards?
1/4 in is the common target for drainage and debris clearance, and the default here. Wet pressure-treated lumber shrinks as it dries, so it's often installed nearly tight; kiln-dried wood and composite need the gap left at install time per the manufacturer.
Can I use 24 inch joist spacing for my deck?
Only in limited cases — 16 in on center is the standard for wood decking laid perpendicular to joists, and many composite boards require 16 in or less. 24 in spacing saves joists but is generally limited to thicker (2x) decking; diagonal decking usually needs 12 in.
Is my deck plan uploaded anywhere?
No. Board, joist, and screw counts are computed entirely in your browser — your deck dimensions are never sent to a server.