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Deck Calculator

Estimate a rectangular deck's surface boards, framing, footings, railing, fasteners, labor, and cost scenarios. Structural design must still be verified locally.

22-calculator project library Reviewed 2026-07-25Calculations run privately in your browser

Enter project details

Example values are prefilled
Deck geometry
ft
ft
in
in
ft
in on center
%
ft
Cost assumptions
$
$
$
$
Location and tax assumptions

The location factor adjusts labor only. Replace all default prices with actual local quotes before purchasing.

A coarse planning adjustment—not a ZIP-code quote.

%

Enter the tax rate that applies to taxable materials.

All default prices are editable examples. Cost scenarios vary the entered plan; they do not represent bids or guarantees.

How to use this deck calculator

Estimate deck boards, linear footage, joists, footings, railing, waste, material cost, and labor.

Formula

Decking linear feet = deck area ÷ effective board width in feet. Boards = linear feet ÷ stock length, plus waste, rounded up. Joists are based on deck width ÷ spacing plus an edge joist.

Worked example

Example: A 16 × 12 ft deck is 192 sq ft. A 5.5 in board with a 1/8 in gap covers an effective 5.625 in width, requiring roughly 410 linear ft before waste.

Accuracy and limitations

This is a material-planning estimate, not a structural design. Beam sizes, joist spans, ledger attachment, lateral loads, stairs, guards, frost depth, and permits require code-compliant design.

Frequently asked questions

Which direction do deck boards run?

The calculator assumes boards run along the entered deck length and joists run beneath them across the width.

Are stairs included?

No. Stairs and landings should be estimated separately.

How many footings are needed?

The calculator gives a planning count based on a coarse grid; final footing locations depend on structural loads and code.

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