Deck board gap layout estimator

Deck Board Spacing Calculator

Estimate deck board rows, equal gap, finished width, board footage, and rough fastener count from deck width, board width, target gap, and deck length.

Units

Deck width across boards (ft)Deck length of boards (ft)Board width (in)Target gap (in)Waste / cuts (%)Cost per board row ($)

Board rows

Equal gap

Finished width

Rough cost

Deck gaps depend on the product and moisture

This calculator lays out board rows and gaps. Board movement, wet lumber, composite manufacturer rules, drainage, hidden fasteners, picture-frame borders, and local code can change the actual installed spacing.

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Deck board spacing formula

Target module = board width + target gap

Board rows = deck width ÷ target module, rounded up

Equal gap = (deck width - rows × board width) ÷ spaces

Board footage = rows × deck length × (1 + waste %)

Sample takeoff

A 12 ft wide deck with 5.5 in boards and a 0.25 in target gap needs 25 board rows, leaving about 0.27 in equal gaps across the width.A 3.6 m wide deck with 140 mm boards and a 6 mm target gap needs 25 board rows, leaving about 4 mm equal gaps across the width.

Deck Board Spacing Calculator FAQ

How does this deck board spacing calculator work?+

It multiplies measured job dimensions by the coverage, spacing, or package yield you enter, adds waste, then rounds the buy quantity up. Use the board manufacturer gap range and the lumber moisture condition before choosing a target gap.It multiplies measured job dimensions by the coverage, spacing, or package yield you enter, adds waste, then rounds the buy quantity up. Use the board manufacturer gap range and the lumber moisture condition before choosing a target gap.

Should I use the default waste value?+

Use the default for a quick planning estimate, then raise it for cuts, odd layouts, breakage, bad access, or product-specific loss.Use the default for a quick planning estimate, then raise it for cuts, odd layouts, breakage, bad access, or product-specific loss.

Is this a bid or code approval?+

No. It is a material planning calculator. Verify product data, local code, structural requirements, electrical requirements, and supplier packaging before ordering or building.No. It is a material planning calculator. Verify product data, local code, structural requirements, electrical requirements, and supplier packaging before ordering or building.