Calculate deck boards, joists, footings, and costs for pressure treated, cedar, composite, and PVC decking. Get a complete material list and cost estimate.
Ready to calculate
Select a material and enter dimensions
| Material | Board Size | Cost/sqft | Lifespan | Maintenance |
|---|---|---|---|---|
| Pressure Treated | 5/4×6" | $3.5/sqft | 10-15 years | High |
| Cedar | 5/4×6" | $6/sqft | 15-20 years | Medium |
| Composite Standard | 1"×5.5" | $8/sqft | 25-30 years | Low |
| Composite Premium | 1"×5.5" | $13/sqft | 30-50 years | Very Low |
| PVC | 1"×5.5" | $10/sqft | 25-30 years | Very Low |
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How many deck boards do I need?
Divide deck width (inches) by 5.625" (board + gap), multiply by boards per row (length / board length), then add 10-15% for waste.
How far apart should joists be?
16" OC is standard. Use 12" OC for diagonal layouts or composite over long spans. 24" OC only for 2x6 boards.
How much does a deck cost?
Materials: $3.50-13/sqft depending on material. Add $20-28/sqft for professional labor. A 12x16 PT deck DIYs for ~$2,500-3,500.
How many footings does a deck need?
One footing every 6-8 feet along beam lines. A 12x16 deck typically needs 3-4 footings, each using 3 bags of 80lb concrete.
Do I need a railing?
Code requires railings when the deck is 30+ inches above grade. Railings must be 36" minimum height with balusters no more than 4" apart.
Pressure treated vs composite?
PT costs less upfront ($3.50 vs $8-13/sqft) but needs annual maintenance. Composite lasts 25-50 years with no maintenance — lower lifetime cost for 15+ year decks.
Enter your deck dimensions, select a material, and choose your options. The calculator determines total area, then calculates board count based on effective board width (5.5" + 1/8" gap), joist count from spacing, posts from beam spans, and concrete bags for footings. Stairs and railing are calculated separately based on deck height and perimeter.
Calculate Area
Area = Length x Width (+ secondary section if L-shape)
Board Count
Rows = ceil(width_in / 5.625) x boards/row x (1 + waste%)
Framing & Footings
Joists = floor(length_in / spacing) + 1 | Posts = ceil(length / 8) + 1
Key Formulas
Boards = ceil(width_in / 5.625) x ceil(length / board_len) x (1 + waste)
Joists = floor(length_in / joist_spacing) + 1
Concrete bags = posts x 3 (80lb each)
Stair steps = round(height_in / 7.5)