Deck Cost Calculator — Estimate Materials and Total Cost

Financial Calculator

How This Material Calculator Works

This calculator uses industry-standard formulas to estimate the quantity of materials needed for your project. It factors in standard waste allowances (typically 5-10% depending on material type) so you purchase enough without significant overbuying. Measurements are based on common product dimensions available at major retailers and building supply stores. For best results, measure your project area carefully and round up to the nearest whole unit when purchasing.

Tips for Accurate Material Estimates

Always measure twice before ordering materials. Account for cuts, corners, and irregular shapes by adding 10% extra for most materials. For concrete and masonry, consider the subgrade preparation and drainage requirements. Check local building codes before starting any project — permits may be required for structural work, fencing over certain heights, or decks above ground level. Buy materials from the same batch to ensure color consistency, especially for tiles, pavers, and paint.

Deck Cost by Size — 12x16, 16x20, 20x20

Installed deck prices in 2026 run $25–$45 per square foot for pressure-treated (PT) pine and $40–$70 per square foot for composite brands like Trex, TimberTech, and Fiberon — figures that include labor, framing, footings, and standard railing. Applied to the three most-quoted sizes: a 12x16 deck (192 sq ft) runs $4,800–$8,600 in PT or $7,700–$13,400 in composite; a 16x20 (320 sq ft) runs $8,000–$14,400 PT or $12,800–$22,400 composite; a 20x20 (400 sq ft) runs $10,000–$18,000 PT or $16,000–$28,000 composite. Cedar and redwood land between the two at roughly $30–$55 per square foot installed. On a mid-range $6,700 12x16 PT build ($35 per sq ft), the budget splits roughly as: framing and footings $1,700 (25%), decking boards $1,500 (22%), railing and stairs $1,000 (15%), and labor $2,500 (38%). Composite shifts that mix because the boards themselves cost $5–$13 per square foot in materials versus $2–$5 for PT — the surface material moves your total more than any other single choice. Per-square-foot rates also fall slightly as decks grow, since fixed costs like permits and contractor mobilization spread across more area; that is why a 20x20 rarely costs double a 12x16 quote from the same builder.

What Moves Deck Cost Most

Five variables swing a deck quote more than material choice alone. Height and stairs: decks more than 30 inches above grade need code-compliant guardrails under IRC R312, and an elevated 8-foot deck adds 20–30% for longer posts, deeper footings, and a staircase priced at $150–$300 per step — a 12-step run alone adds $1,800–$3,600. Railing linear feet: wood rails run $30–$60 per linear foot installed, composite $60–$120, and aluminum or cable systems $80–$150; a typical attached 12x16 deck needs about 40 linear feet, a $1,200–$6,000 swing on one line item. Permits: most US municipalities charge $150–$800 for a deck permit, and attached or elevated decks almost always require one — some cities also demand stamped footing plans. Demolition: tearing out an existing deck costs $5–$15 per square foot including disposal, or $960–$2,880 for an old 12x16. Region: total installed prices in coastal metros such as Boston, Seattle, and the Bay Area run 20–40% above the national ranges shown here, while much of the rural Midwest and South lands 10–15% below. Get the railing spec and stair count in writing before signing — those are the two items contractors most often underscope in a first estimate.