Deck Calculator
Calculate how many deck boards you need for your deck project including waste factor.
How many deck boards do I need?
Calculate deck area (Length x Width), divide by board coverage area, add waste. Standard deck boards: 5.5" wide (actual width of 2x6), lengths 8', 10', 12', 16'. Example: 16'x12' deck = 192 sq ft. Using 12' long 2x6 boards (5.5" = 0.458 ft): 12 x 0.458 = 5.5 sq ft per board. Need 192 / 5.5 = 35 boards + 15% waste = 41 boards. Account for rim joists, fascia separately.
What size lumber do I need for deck joists and beams?
Joist sizing by span (16" spacing typical): 6-8' span: 2x6, 8-10' span: 2x8, 10-12' span: 2x10, 12-16' span: 2x12. Beam sizing depends on span and load - typically double 2x8 or 2x10. Use pressure-treated lumber for structure, cedar/composite/PT for decking. Joist spacing: 16" on-center standard, 12" for composite decking. Always consult local codes - spans vary by species, grade, and load requirements.
Should I use pressure-treated, cedar, or composite decking?
Pressure-treated (PT): Cheapest ($2-4/sq ft), requires annual maintenance, splinters possible, 20-25 year life. Cedar: Mid-price ($4-8/sq ft), naturally rot-resistant, beautiful, needs sealing every 2-3 years, 20-30 years. Composite: Highest cost ($8-12/sq ft), no maintenance, no splinters, fades slightly, 25-50 year warranty. Best choice depends on budget and maintenance preference. PT for structure always, decking surface is personal choice/budget.
How do I calculate materials for deck railings and stairs?
Railing: Measure linear feet of edges needing rails, multiply by 3-4 ft for posts/balusters per section. Typical: Posts every 6 ft, balusters 4" apart (code). Example: 40 linear ft perimeter = 7 posts + 120 balusters + top/bottom rails. Stairs: 7-7.5" rise per step (code), calculate total rise (deck height), divide by 7.5 for number of steps. 10" tread depth standard. Add stringers (usually 3 per stair width).