Deck Board Calculator

Estimate the number of deck boards, board rows, linear footage, fasteners, waste allowance, and material cost for a rectangular deck.

Deck Dimensions

Deck Length (ft)

Deck Width (ft)

Board Direction

Deck boards normally run perpendicular to the joists. Board direction affects the required board length and the number of rows.

Deck Board Details

Actual Board Width (in)

Gap Between Boards (in)

Stock Board Length (ft)

Waste Allowance (%)

A nominal 6-inch deck board is commonly about 5.5 inches wide. Confirm the actual width and recommended spacing for your selected wood or composite product.

Fasteners & Cost

Joist Spacing On Center (in)

Fasteners Per Board at Each Joist

Price Per Stock Board ($)

Fasteners Per Package

Price Per Fastener Package ($)

Decking Estimate

Deck Area —

Board Run Length —

Number of Board Rows —

Boards Per Row —

Base Stock Boards —

Waste Allowance —

Total Stock Boards —

Total Board Length Purchased —

Estimated Fasteners —

Fastener Packages —

Estimated Decking Cost —

Estimated Fastener Cost —

Estimated Material Cost —

This estimate assumes straight, parallel decking on a rectangular deck. Picture framing, diagonal layouts, breaker boards, stairs, fascia, blocked seams, unusual shapes, and manufacturer requirements may increase the material needed.

How the Deck Board Calculator Works

The calculator uses the actual board width plus the selected gap to determine how many rows cover the deck. It then determines how many stock boards are required for each row and adds the selected waste allowance.

Board Rows = Deck Coverage Width ÷ (Board Width + Gap)

Which Direction Should Deck Boards Run?

Deck boards normally run perpendicular to the supporting joists. The chosen direction determines the distance each row must travel and the dimension across which the board rows are placed.

How Much Space Should Be Between Deck Boards?

Required spacing depends on the decking material, moisture content, temperature, drainage needs, and manufacturer instructions. Wood may change width as it dries or absorbs moisture. Composite products often have specific spacing requirements.

How Much Waste Should You Add?

Ten percent is a useful planning allowance for many simple rectangular decks. Diagonal boards, picture-frame borders, complex shapes, defects, damaged boards, and pattern matching may require a larger allowance.

Estimating Deck Fasteners

The fastener estimate uses the number of board rows, the board run length, joist spacing, and fasteners installed at each board-and-joist intersection. Hidden-fastener systems and specialty decking may use different quantities.

Before Purchasing Materials

Confirm board dimensions, available stock lengths, joist spacing, span limits, fastening requirements, stair details, local building requirements, and the final layout before ordering materials.