Free decking calculator for 2026 — estimate deck boards by length, joist spacing, screws & hidden fasteners, waste and cost for pressure-treated, composite, PVC and hardwood. Straight 90°, diagonal 45° and herringbone pattern. Live results, no signup, runs in your browser.
Live estimating — boards, waste & fasteners
Boards run along length • e.g. 16 ft 0 in × 12 ft 0 in
Auto: 192.00 sq ft — custom for L-shape/irregular
Using: 192.00 sq ft
Auto: 56.00 ft • fascia / rim joist
Net width: 5.5"
Default gap 0.125" • Coated deck screws
Optimizer picks best mix to minimize waste
Enables cost estimate (boards × price)
2 screws / joist • 1 clip / joist • joists = floor(len/spacing)+1
Angle waste added on top of base waste
Effective width: 5.625" (net + gap)
Total = 10% + 0% angle = 10%
| Board | Required | Waste % | Req + Waste |
|---|---|---|---|
| 16' | 26 | 10% | 29 |
Add board price / linear ft to see cost (v2).
Effective width = net 5.5" + gap 0.125" = 5.625"
Rows = ceil(width 144.0" / 5.625") = 26
Linear ft = rows × 16.00 ft = 416 ft
Waste = base 10% + angle 0% = 10%
Estimates only. 1 clip / joist / board.
A decking calculator (also called a deck board calculator or deck material calculator) converts your deck size into a bill of materials: how many deck boards of each length, total linear feet, waste %, deck screws and hidden fasteners, and an optional deck cost estimator. Unlike a simple square-footage divider, this decking quantity calculator accounts for actual board width (nominal vs actual: 1×6 = 5.5″), gap between boards (1/8″ wood, 3/16″ composite), joist spacing (12″/16″/24″ o.c.), decking angle and board-length availability — so you don’t over- or under-order.
Use it as a composite decking calculator for Trex-style boards, a pressure-treated deck calculator, PVC or exotic hardwood estimator, and as a deck cost calculator by entering price per linear foot. It also works as a deck square footage calculator and perimeter calculator for fascia and rim joists. See Bob Vila’s wood-deck planning guide for nominal vs actual sizes.
Deterministic, pure TypeScript — same decking calculator inputs always give same outputs. See “How we calculated” inside live results for per-input transparency.
effectiveWidth = netBoardWidth + gap rows = ceil(deckWidthIn / effectiveWidth) // e.g. 144" / 5.625" linearFt = rows × deckLengthFt // e.g. 26 × 16 = 416 ft waste% = baseWaste + angleExtra // 90° +0% | 45° +12% | herringbone +22% joists/board = floor(boardLenIn / joistSpacing) + 1 // 192"/16"=12+1=13 screws/board = joists × 2 // 13×2=26 clips/board = joists × 1 // 13×1=13 req+Waste = ceil(required × (1+waste%)) // 26×1.10=29
Board-length mix is optimized per row via DP: minimal overcut, then minimal count. Totals aggregate across rows and future L-shape sections.
Enter deck length and width in ft + in. This deck square footage calculator auto-computes total sq ft = L×W and perimeter = 2×(L+W) — both editable for irregular or L-shaped decks. Boards run along length.
Pick board size: 1×4 (3.5″), 1×6 / 5/4×6 / 2×6 (5.5″), 2×8 (7.25″) or custom. Material sets default gap between boards and fastener: pressure-treated 1/8″ screws, composite/PVC 3/16″ hidden clips.
Joist spacing (12″ for composite, 16″ standard, 24″) drives deck screws and hidden fasteners. Decking angle adds waste: straight 10%, diagonal +12%, herringbone/chevron +22%.
Table: board length, required, waste %, and required + waste. Summary: total boards, linear feet + waste, screws, clips, and optional deck cost estimator (price × linear ft).
Use this decking boards calculator reference to compare nominal vs actual widths and see coverage. Standard 6″ nominal = 5.5″ actual is the most common composite decking calculator width.
Decking is sold by nominal size; actual net width drives coverage. Gap added to get effective width.
| Material / Size | Gap / Size | Notes |
|---|---|---|
| 1×4 | Actual 0.75" × 3.5" | 3.5″ coverage |
| 1×6 / 5/4×6 / 2×6 | Actual 5.5" face width | 5.5″ coverage (most common) |
| 2×8 | Actual 1.5" × 7.25" | 7.25″ coverage |
| Custom | Any width you set | You define net width |
Each material suggests a gap and fastener. Override freely — defaults match decks.com and Trex guides.
| Material / Size | Gap / Size | Notes |
|---|---|---|
| Pressure-Treated | Gap 1/8" (0.125″) | $1.2–$1.4 / lin ft • Coated screws |
| Composite (Trex-style) | Gap 3/16" (0.1875″) | $3.0–$4.0 / lin ft • Hidden clips |
| PVC | Gap 3/16" (0.1875″) | $4.0–$5.0 / lin ft • Hidden clips |
| Exotic Hardwood (Ipe) | Gap 1/8" (0.125″) | $6–$8 / lin ft • Stainless screws |
| Joist spacing | 12" / 16" / 24" o.c. | 16″ default • 12″ for composite |
Helps you sanity-check any deck board calculator result. Gap 0.125″ assumed; adjust for 0.1875″.
| Board | Actual width | Effective w/gap | Lin ft / sq ft | Waste 10% total |
|---|---|---|---|---|
| 1×4 | 3.5″ | 3.625″ | 3.31 | 3.64 |
| 1×6 / 5/4×6 / 2×6 | 5.5″ | 5.625″ | 2.13 | 2.35 |
| 2×8 | 7.25″ | 7.375″ | 1.63 | 1.79 |
Formula: rows = ceil(width/ effective), lin ft = rows × length. Example 10×12 ft (120 sq ft) with 5.5″ boards needs ~256 lin ft (2.13×120) before waste.
Three real decking calculator scenarios using this deck board calculator. Copy numbers into the tool to verify.
5.5″ + 0.125″ gap • 16 ft boards • 16″ joists • 10% waste
5.5″ + 0.1875″ gap • 8+12 ft mix • 16″ joists • 22% waste
5.5″ + 0.1875″ gap • 12 ft boards • 12″ joists • 32% waste
Pair this decking calculator with its price field for a local deck cost estimator. National 2026 installed averages (planning only): pressure-treated ~$35/sq ft, composite ~$57/sq ft, DIY materials-only ~$20/sq ft. Example: 192 sq ft (12×16) composite at $57 ≈ $10,944 installed; materials-only decking alone ~$3,840 (192×$20). Always get local quotes — two metros in the same state can differ by 15%+.
Sources for planning: Bob Vila – How much does it cost to build a deck? and Decks.com. Use the calculator’s cost output (boards × price per linear ft + fasteners) for your exact total.
Want to double-check the numbers or learn the build steps? These guides cover the details the calculator can’t:
Manufacturer’s gapping (3/16″) and hidden-clip spacing — check before you order.
This Old House — How to build a simple deckFraming, ledger, footings and joist hangers step-by-step for first-time builders.
Bob Vila — Wood deck planning guideChoosing species, maintenance and what to expect from pressure-treated vs cedar.
A DP (unbounded knap) searches for board combinations that cover one row length with minimal overcut (waste), then minimal board count. That per-row mix is multiplied by rows to get totals. Limit available lengths to match your yard’s stock for the most realistic deck material list.
This decking calculator is a planning deck estimator only — actual deck boards, deck screws and waste depend on board quality, crew, and site cuts. Confirm joist spacing and gap between boards with your decking manufacturer (Trex, TimberTech, etc.). No external APIs are used; all math runs client-side for privacy and speed.
Always verify structural requirements with a licensed professional before purchasing materials for your deck building project.
Content Updated: 29/08/2026 • Pure TS engine: lib/deckCalculator.ts • Keywords: decking calculator, deck board calculator, deck cost calculator, composite decking calculator