Deck Calculator

Building a backyard deck? Enter deck length, width, board width, and joist spacing — get deck area, number of decking boards, joist count, post estimate, and screw quantity in seconds. Works for pressure-treated wood, composite, PVC, and tropical hardwood decking.

Deck material searches peak in spring when homeowners plan outdoor living projects. A typical 5 m × 4 m (16 ft × 13 ft) deck covers 20 m² (~215 sq ft) — enough for a table and grill. At 14 cm (5.5") board width, you need roughly 29 boards running the length plus 10% waste for cuts and end gaps.

Joist spacing drives framing cost: 40 cm (16") on center is standard for wood decking; composite manufacturers often require 30 cm (12") for warranty compliance. A 5 m span at 40 cm spacing needs 14 joists plus rim boards — our calculator counts joists automatically from your inputs.

Worked example: 5 m × 4 m deck, 14 cm boards, 40 cm joist spacing → 20 m² surface, ~32 deck boards, ~14 joists, ~7 posts (approx.), ~400 deck screws. Add railing separately — most codes require guardrails when the deck surface is 30"+ above grade.

Cost ballpark (installed, varies by region): pressure-treated wood $150–250/m² ($15–25/sq ft), composite $250–450/m² ($25–45/sq ft). Material-only is roughly 40–50% of installed price. Use this calculator for the material list; get labor quotes locally.

Always check local building codes for footing depth, ledger flashing, guardrail height, and permit requirements. Free calculator — results are planning estimates, not engineered structural drawings.