Deck Square Footage Calculator

Multiply the length by the width of each rectangular section of the deck, then add the sections together. A 16 × 20 ft main deck is 320 sq ft; add a 6 × 8 ft stair landing and you're at 368 sq ft. Subtract anything you're not surfacing — a hot tub footprint, a built-in planter, a tree cutout. For decks with angled corners, curves, or several levels, the section math gets unreliable fast, which is when tracing the real outline on satellite imagery is faster and more accurate.

Most residential decks fall between 200 and 500 square feet. A small entry or landing deck is often 8 × 10 ft (80 sq ft), a common back deck runs 12 × 16 ft (192 sq ft), and one of the most-built sizes is 16 × 20 ft, or 320 sq ft. Wraparound and multi-level decks commonly land between 500 and 900 sq ft. These are ranges rather than standards — measure before you quote.

Not in the floor area. Square footage is the walking surface — the decking boards seen from above. Railings, spindles, stair risers, and fascia are separate surfaces with their own labor, and they matter a lot on a staining job: a deck with 40 linear feet of railing can add hours that the floor square footage never shows. Price the floor by the square foot, then add for railing linear footage and stair count. Stair treads themselves are usually counted as added square footage since you walk on them.

Yes. Draw each level or wing as its own shape and the areas total automatically, so you get both the breakdown and the combined figure. That's the same workflow contractors use for a deck plus a separate landing, or a deck that steps down to a patio.

This is the one real limitation for decks. A deck under a permanent roof, pergola, or dense tree canopy isn't fully visible from above, so you can't trace its whole edge. In that case, trace what you can see and measure the obscured portion by hand, or fall back to length × width for the covered section using the calculator on this page. Open, uncovered decks — the majority of what gets washed and stained — trace cleanly.

On a clear, unobstructed surface, satellite-based measurement typically lands within 1–3% of a physical tape measurement. That's accurate enough to order stain, price labor, and send a professional quote. Decks sit slightly toward the harder end of that range because they're smaller than driveways and often partly shaded, so the edge is worth zooming in on before you close the shape.

Deck washing commonly runs about $0.30–$0.50 per square foot — higher than concrete, because wood and composite need low pressure, a cleaner and brightener, and careful work to avoid furring the boards. Cleaning plus staining or sealing typically runs about $2–$4 per square foot including the prep. On a 320 sq ft deck that's roughly $95–$160 to wash and roughly $640–$1,280 to clean and stain. Published national ranges for a full clean-and-stain span roughly $450 to $1,950 because deck size, railing footage, board condition, and stain grade move the number so much.

Not to produce an estimate. If the deck is visible from above you can measure it, price it, and send the quote from your desk, then confirm details like railing footage and board condition when you arrive to do the work. Many contractors use remote measurement to decide which jobs are worth the drive in the first place.