ProjectSizedSizing answers for home projects — shown with the work.

Deck board calculator

Reviewed 2026-07-04 · Boards, screws and the spacing rules

Quick answer

A standard deck board (5.5″ face + ¼″ gap) covers 0.48 sq ft per linear foot. So a 12×16 deck (192 sq ft) takes about 28 sixteen-foot boards including 10% waste, plus roughly 350 screws per 100 sq ft. Composite on a diagonal needs joists at 12″ on center, not 16″.

Calculator

Rating · MaterialsNO. DCK-01
28 boards
16 ft boards · 10% waste in
Deck area192 sq ft
Screws (2 per joist crossing)≈ 675
Joist spacing16″ on center

Diagonal patterns add cuts: waste is bumped to 15%. Composite brand span charts override this page; check yours before framing.

The coverage math, shown

A "6 inch" deck board is actually 5.5 inches wide. Add a ¼ inch gap and each board occupies 5.75 inches of deck width, which is 0.479 sq ft per linear foot of board. Boards needed = deck area ÷ (board length × 0.479), plus waste. That's the whole formula, and now you can sanity check any calculator, including this one.

Buy the long boards if you can Fewer butt joints means fewer cut ends, less waste, and a cleaner deck. If your deck is 16 ft in one direction, 16 ft boards with zero joints beat 12 ft boards with a joint line down the middle, even at a higher price per foot.

Frequently asked

How many deck boards do I need for a 12x16 deck?

That is 192 sq ft. With standard 5.5 inch wide boards and a 1/4 inch gap, each 16 ft board covers about 7.7 sq ft, so you need 25 full-length boards, call it 28 with 10 percent waste. Using 12 ft boards instead: about 37 with waste.

How many screws per deck board?

Two screws per board at every joist. With joists 16 inches on center, a 16 ft board crosses 13 joists: 26 screws per board. Rule of thumb: about 350 screws per 100 sq ft of decking.

What joist spacing for composite decking?

16 inches on center for straight composite runs, 12 inches for diagonal patterns, and some brands require 12 inches regardless. Wood decking is fine at 16 inches. Check your specific brand’s span chart; it overrides everything, and skipping it can void the warranty.

What gap between deck boards?

About 1/4 inch for dry wood and composite (composite brands specify exactly, often 3/16 to 1/4 inch side gap). Pressure-treated lumber that is still wet gets installed nearly tight; it shrinks to a gap as it dries.

Related tools

Concrete bag chart

Footings for the deck posts.

Fence post spacing

Same yard, next project.

Sources