Deck Calculator — m, boards, joists, cost
How to use this calculator
Enter deck dimensions in meters, centimeters, or millimeters using the unit dropdown. Choose rectangle or L-shape, select decking board profile, joist size and spacing, beam and post configuration, and waste allowance. Results update instantly with material counts, timber volume in m³, and an interactive plan view.
Cost — enter price per board, per joist, per beam, per post. Select your currency (EUR, PLN, CZK, SEK, etc.).
Hardware — joist hangers, post bases, screws (kg), and coach bolts are estimated automatically based on the framing layout per EN 1995-1-1.
Saved Calculations
| Time | Shape | Area m² | Boards | Joists | Beams | Posts | m³ | Total |
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How to Calculate Materials for a Timber Deck
This deck calculator estimates the number of decking boards, joists, beams, posts, and hardware needed for a rectangular or L-shaped timber deck per EN 1995-1-1 (Eurocode 5). Enter dimensions in meters, centimeters, or millimeters, select timber profiles and board lengths, set joist spacing (300, 400, or 600 mm on centre), and adjust waste allowance from 5% to 20% depending on layout complexity.
Formulas
Decking boards = deck span perpendicular to boards / (board face width + gap), rounded up. Each board must span the parallel dimension; partial lengths require additional boards per row.
Joists = (span / spacing) + 1, plus 2 rim joists. Beams run perpendicular to joists with posts at the specified spacing. Timber volume = width x depth x length for each piece, summed in m³.
Screws ≈ 22 screws per m² (about 1 kg per 200 stainless steel 5 x 60 mm screws). Joist hangers = 1 per joist. Coach bolts = 2 per beam-to-post connection.
Tips
Standard 140 x 22 mm profiles are suitable for residential decking at 400 mm joist spacing. Use 145 x 28 mm for heavy traffic or 600 mm spacing. 45 x 190 mm joists span up to 3.6 m; 45 x 240 mm joists span up to 4.8 m. Double beams allow longer post spacing. Always use pressure-impregnated softwood (class UC3/UC4) or naturally durable species (oak, larch, thermowood) for outdoor exposure per EN 335.
FAQ
What spacing for composite decking? Most composite manufacturers require 400 mm o.c. joist spacing (some allow 300 mm for diagonal installation).
How much waste for a simple rectangle? 10% is standard. Add 15-20% for angled or herringbone patterns.
Should I use double rim joists? Double rim joists are recommended for decks wider than 3.6 m or when supporting stairs.
