Deck Material Calculator
Calculate decking, framing lumber, posts, concrete, fasteners, and railing materials for any deck size.
Ground to top of deck frame
0 = auto (perimeter minus house side)
Estimated Material Cost
$1,244
192 sqft · Pressure Treated · $6/sqft
Deck Boards
| Deck Area | 192 sqft |
| Boards Per Row (5.5" (nominal 2×6)) | 27 |
| Total Deck Board LF (w/ 10% waste) | 475 lf |
| Decking Cost (475 lf × $1.50) | $713 |
Framing
| Joists (16" OC (standard)) | 13 × 12 ft = 156 lf |
| Beams (doubled, every 8 ft) | 3 × 16 ft = 48 lf |
| Posts 6×6 (5.0 ft ea, 2 ft in ground) | 9 posts = 45 lf |
| Total Framing LF | 249 lf |
| Concrete 80 lb Bags (2 per post) | 18 |
| Framing Cost (249 lf × $1.50) | $374 |
Fasteners & Railing
| Deck Screws / Nails (10 lbs) | $50 |
| Concrete (18 bags × $6) | $108 |
| Railing Posts (every 6 ft) | 8 posts |
| Rails (top + bottom) | 80 lf |
| Balusters (4" spacing) | 107 |
| Cost Summary | Amount |
|---|---|
| Decking (Pressure Treated) | $713 |
| Framing Lumber (PT) | $374 |
| Concrete | $108 |
| Fasteners | $50 |
| Total Material Cost | $1,244 |
| Cost Per Sqft | $6/sqft |
Mike Callahan:Composite decking is 3× the material cost of PT but zero maintenance for 25 years. Do the math on 25 years of staining PT every 2–3 years ($2–3/sqft per application) and composite wins. But always frame with pressure treated, even under composite — composite joists don’t exist.
Boards per row = deck width ÷ board width. Total LF = boards × length × 1.10 waste. Joists = length ÷ spacing + 1, spanning the width. Beams every 8 ft, doubled 2×10. Posts at each beam intersection, extending deck height + 2 ft underground. Concrete at 2 bags (80 lb) per post. Fasteners at 5 lbs/100 sqft for screws or 3 hidden clips/sqft for composite. Framing priced at $1.50/lf (pressure treated). Railing posts every 6 ft, balusters at 4-inch spacing. Costs are material only — labor typically adds 50–100% for professional installation.
Frequently Asked Questions
How many deck boards do I need?
Divide the deck width by the board width to get boards per row, then multiply by the deck length for total linear feet. Add 10% for waste from cuts and defective boards. For a 16×12 ft deck with 5.5-inch boards: 12 ft ÷ 0.458 ft = 27 boards per row × 16 ft = 432 lf, plus 10% waste = ~475 lf. If buying 16-ft boards, that’s 27 boards with minimal waste.
16-inch vs 12-inch joist spacing?
Standard 16-inch on-center spacing works for most wood decking with 2×6 boards. Use 12-inch spacing for composite and PVC decking (most manufacturers require it for warranty), diagonal board patterns, hot tub or heavy-load areas, and spans over 10 feet between beams. The 12-inch spacing uses about 33% more joist lumber but prevents bounce and flex.
Pressure treated vs composite cost over time?
Pressure treated lumber costs $1.50–2.00/lf upfront but needs staining every 2–3 years at $2–3/sqft. Over 25 years, a 200 sqft PT deck costs roughly $600 in lumber + $4,000–6,000 in stain and labor. Composite costs $5–7/lf upfront with zero maintenance — the 25-year total is often comparable or less than PT when you factor in your time and materials. PT also has a 15–20 year lifespan vs 25–30 for composite.
How deep should deck post holes be?
Deck post holes must extend below the frost line, which varies by region: 12 inches in the South, 36–48 inches in the Northern US and Canada. As a minimum, IRC code requires footings at least 12 inches below undisturbed ground. Most jurisdictions require 42–48 inches for frost protection. The hole diameter should be 3× the post width — for a 6×6 post, dig a 16–18 inch diameter hole. Always check local code before digging.
How the Deck Material Calculator works
The deck material calculator turns a deck length, width, height, board type, and joist spacing into a full material takeoff: decking, framing lumber, posts, concrete, fasteners, and railing, plus an estimated material cost.
Decking is figured by rows. Boards per row = deck width ÷ board width (5.5 inches for a 2×6, or 3.5 inches for a composite plank), rounded up. Total decking length = boards per row × deck length × 1.10, adding 10% for cutting waste. Joists = deck length ÷ joist spacing (16 or 12 inches on center) + 1, each spanning the deck width. Beams are placed every 8 feet across the width, running the full length as doubled members. Posts sit at each beam intersection, and each post length is deck height + 2 feet to account for the portion set in the ground.
Concrete is estimated at 2 eighty-pound bags per post. Fasteners for wood decking are figured at about 0.05 lbs per square foot (5 lbs per 100 sq ft), while composite and PVC decks instead use 3 hidden clips per square foot. Railing (the length you enter, or the perimeter minus the house side by default) drives railing posts every 6 feet, top and bottom rails, and balusters at 4-inch spacing. Costs use the per-linear-foot price of the chosen decking material, $1.50/lf for pressure-treated framing, and $6 per concrete bag.
Worked example: a 16 ft × 12 ft pressure-treated deck (192 sq ft) with 5.5-inch boards, 16-inch joists, and 3 ft height needs 27 boards per row, about 475 linear feet of decking, 13 joists, doubled beams, 9 posts, and 18 bags of concrete, landing near $1,244 in materials, or roughly $6.50 per square foot before labor.
Frequently Asked Questions
How does the calculator estimate framing lumber?
It totals the joists, beams, and posts in linear feet, then prices them at $1.50 per linear foot for pressure-treated lumber. Joists span the width and repeat every 12 or 16 inches, beams are doubled members every 8 feet, and posts run the deck height plus 2 feet for the buried portion. Even under composite decking the framing is always pressure-treated, because composite joists do not exist.
How many bags of concrete does the calculator budget per post?
Two 80 lb bags per post, priced at $6 per bag. A deck with 9 posts therefore needs 18 bags. This covers a typical footing; deeper frost-line footings in northern climates may need more, so treat it as a baseline.
How is railing material calculated?
If you leave railing length at 0, the tool defaults to the perimeter minus one long side against the house, which is deck length + 2 × width. From that length it sets a railing post every 6 feet plus one, top and bottom rails at 2 × railing length, and balusters at 4-inch spacing.
What does the cost estimate include?
It sums decking, pressure-treated framing, concrete, and fasteners into a material-only total and divides by the deck area for a cost per square foot. It does not include labor, which typically adds 50 to 100% for professional installation, nor stairs, hardware, or permits.