Deck Material Calculator
Estimate decking boards, joists, screws, and stain from the deck footprint and board spacing. It is a planning estimate, not an engineered deck design.
A 12 by 16 ft deck with 5.5 in boards and 16 in joist spacing needs about 26 16-ft boards, 13 joists, 676 screws, and 1.5 gal of stain.
How to use it
- Enter deck size. Add deck length and width in feet.
- Set the board details. Use the actual board width, gap, and stock length you plan to buy.
- Choose joist spacing. Pick 12, 16, or 24 inches on center, then check local code and board instructions.
- Read the material list. Use boards, joists, screws, and stain gallons as a planning estimate before you buy or build.
How this works
Boards across are deck width in inches divided by board width plus gap, rounded up. Total board lineal feet are boards across times deck length, then boards needed are rounded up by stock length. Joists are deck length in inches divided by joist spacing, rounded up plus one. Screws are two per board and joist crossing. Stain is deck area times two sides, divided by about 250 sq ft per gallon.
Sources
Joist spacing references include TimberTech deck joist spacing guidance, Decks.com joist spacing guidance, and Trex joist installation guidance. Fastener assumptions follow Fiberon decking installation instructions. Stain quantity is checked against Olympic stain coverage guidance.
Deck material questions
How many deck boards do I need?
The calculator divides deck width in inches by board width plus gap, rounds up to boards across, multiplies by deck length for lineal feet, then rounds up by stock length.
How many screws does a deck need?
This estimate uses two screws per board and joist crossing. Hidden fastener systems, picture frames, stairs, borders, and waste can change the count.
Is 16 inch joist spacing always right?
No. Sixteen inches on center is common, but some decking, diagonal layouts, heavy loads, or local code can require 12 inches. Confirm before you build.
Why does the stain estimate double the deck area?
The handoff formula uses deck area times two sides, divided by about 250 sq ft per gallon. The actual can label and wood condition should override this planning estimate.
Can this design my deck structure?
No. It is a material planning estimate, not an engineered design. Check spans, ledgers, beams, footings, permits, and local code before building.