Decking is the most expensive part of a deck — underbuy and you lose a weekend, overbuy and you burn budget. Enter your deck size for an exact board count, linear feet and screw estimate, waste included.
Your deck
How the math works
Each board covers its width plus one gap. The calculator divides your deck width by that coverage to get the number of rows, multiplies by deck length for linear feet, then converts to boards of your chosen length:
Rows = deck width ÷ (board width + gap) · Boards = (rows × deck length × 1.10) ÷ board length, rounded up
Tips before you order
- Wet pressure-treated shrinks. Install wet PT boards almost touching; they’ll open to ~¼″ as they dry. The gap selector has a wet-PT setting for a reason.
- Match board length to deck length where you can — a 16 ft deck with 16 ft boards has zero butt joints and far less waste.
- Adding stairs? Lay them out with the stair calculator, and fence the yard with the wood fence calculator.
- Price the lumber by volume for odd sizes with the board foot calculator.
Frequently asked questions
How many boards do I need for a 12×16 deck?
With 5.5″ boards and a ¼″ gap: 26 rows × 16 ft = 416 linear feet. Buying 16 ft boards with 10% waste, that’s 29 boards — exactly what the calculator shows with its default settings.
What gap should deck boards have?
Aim for about ¼″ after drying for drainage and debris. Dry (kiln-dried or composite) boards are installed with the final gap; wet pressure-treated boards are installed tight and shrink to the gap.
How many screws does a deck need?
Two screws at every joist crossing. A 16 ft board on 16″ joist spacing crosses 13 joists = 26 screws per board. The calculator totals this for your whole deck.
Can I run boards diagonally?
Yes, but increase waste to 15–20% and use 12″ joist spacing — diagonal boards span further between joists. This calculator assumes boards run parallel to the length side.