Surface area
length × widthFinds the finished horizontal deck surface.
Inputs
Adjust the project details to update the estimate.
Planning estimates use standard formulas. Verify quantities with your supplier before ordering.
Estimate
Map the deck before you price it.
Deck surface
Finished walking area before stairs and borders.
192 sq ft
Deck boards
Board quantity based on exposure and a cutting reserve.
26
Joists
A preliminary count using common framing spacing.
13
Posts and footings
An early support estimate that is not structural engineering.
8
Material range
A planning window by decking material.
$3,456–$8,064
Surface area: length × width
Estimates use standard planning formulas. Verify quantities with your supplier or contractor before ordering.
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Deck Calculator
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How to estimate deck materials
Begin with the finished length and width. Surface area drives board quantity, but spans, beam layout, stairs, railing, ledger attachment, and local code determine the actual frame.
Board exposure matters more than nominal width because gaps and edge details change the number of rows. Add separate allowances for picture-frame borders, stairs, fascia, fasteners, and waste.
Treat this calculator as a planning aid, not a permit drawing. A ledger, guard, footing, and stair design may need local review or an engineer depending on the site.
Formulas used
Board rows
width × 12 ÷ board_exposureConverts width to inches and divides by the visible board exposure.
Joist count
length × 12 ÷ spacing + 1Provides a preliminary count at the selected on-center spacing.
Frequently asked questions
What to know before you order.
Does the deck estimate include stairs?
No. Stairs, landings, railing, fascia, and their framing should be measured separately.
Are sixteen-inch joist centers universal?
No. Sixteen inches is common, but composite boards, diagonal layouts, spans, and local code may require another spacing.
Will this size a footing?
It provides a planning quantity only. Soil, loads, frost depth, beam spans, and code determine actual footing design.
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