Homeowners type that question into a search box and get a range like “$25–$55 per square foot.” Deck builders hear the same number on the phone. The range is not a bid. A 14×20 patio ten inches off grade and a 14×20 elevated deck eight feet up are the same 280 square feet and completely different jobs.
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Height above grade. Around 30 inches, a typical residential guard comes into play. Higher still, you are setting more posts, buying more framing, and spending time on fall protection. None of that is in the square footage.
Railing lineal feet. Rail is a lineal-foot product. On an elevated deck it is often a large share of the ticket. Zero lineal feet on a guard-height takeoff is the square-foot rule hiding a real line.
Stairs. Each run is stringers, treads, and usually more rail. It is carpentry, not a rounding error on the deck square footage.
Material system. Pressure-treated pine, cedar, and composite are different tickets and different hours. Composite waste and hidden fasteners do not behave like a PT 5/4 board.
Tear-out. An existing deck is disposal plus labor. A postcard special priced as “new only” still has to haul the old one.
The calculator does that arithmetic in your browser. Starting material prices and hours are ballpark figures you replace with your own tickets. It is not a building-code table, a stamped structural calculation, or a permit finding.
A 14×20 main deck and a 10×12 wrap, both 3 feet off grade, in pressure-treated pine, with 46 lineal feet of wood rail, one 4-foot stair (5 risers), and 280 square feet of tear-out. A $28-a-foot special on that 400-square-foot footprint is $11,200. Once height, rail, stairs, demo, loaded labor, and overhead are on the page, that number is often underwater. The calculator shows the walk-away and the margin a proposed price actually leaves.
There is no universal price per square foot. A defensible bid starts from each surface's area, height above grade, and material, then adds railing lineal feet, stair runs, tear-out, loaded labor, overhead, and the margin you intend to keep. The walk-away number is total cost — below that the job loses money.
Two decks of the same footprint are different jobs once one is 10 inches off grade and the other is 8 feet up. The elevated deck needs more posts, usually a guard, fall-protection time, and often stairs. Railing is priced by the lineal foot, not by the deck square footage.
No. The height and guard notes are ballpark estimating aids, not an IRC table, a stamped calculation, or a permit finding. Confirm measurements, footing layout, guard and stair requirements, and pricing with a qualified professional before bidding or building.