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Free decking calculator for 2026. Enter deck size and it estimates boards by length, joist spacing, screws and hidden fasteners, waste and cost. It handles pressure-treated, composite, PVC and hardwood in straight, diagonal and herringbone layouts. Results update live in your browser, no signup.
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 turns deck size into a materials list. You get how many boards of each length, total linear feet, waste percent, screw and hidden fastener counts, and a cost estimate if you add a price. Unlike a simple area divider, it uses actual board width. A nominal 1 by 6 is 5.5 inches. It also uses the gap between boards (1/8 inch for wood and 3/16 inch for composite), joist spacing at 12, 16 or 24 inches on center, layout angle and what lengths your yard stocks. That keeps you from ordering too much or too little.
You can use it for Trex style composite, pressure-treated pine, PVC or hardwood, and for square footage and perimeter for fascia. See Bob Vila wood-deck planning guide for nominal versus actual sizes. Details on deck construction help if this is your first build.
Same inputs always give same outputs. Open How we calculated in the results to see each step for your inputs.
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
The tool picks the board mix per row with the least overcut, then the fewest boards. Totals add up across rows.
Enter length and width in feet and inches. Square feet equals length times width, perimeter equals 2 times length plus width. You can edit both for L shaped decks. Boards run along the length.
Pick 1 by 4 at 3.5 inches, 1 by 6 or 5/4 by 6 or 2 by 6 at 5.5 inches, 2 by 8 at 7.25 inches, or custom. Pressure-treated defaults to 1/8 inch gap with screws. Composite and PVC default to 3/16 inch gap with hidden clips.
Joist spacing is 12 inches for composite, 16 inches standard, 24 inches economy. It sets screw and clip counts. Waste defaults to 10 percent for straight, plus 12 percent for diagonal and plus 22 percent for herringbone or chevron.
The table shows board length, required count, waste percent and required plus waste. The summary shows total boards, linear feet with waste, screws, clips and cost when you enter price per linear foot.
Nominal size differs from actual width. A nominal 6 inch board measures 5.5 inches, the common width for composite boards. Check the table for actual widths and coverage.
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 to $1.4 / lin ft • Coated screws |
| Composite (Trex-style) | Gap 3/16" (0.1875″) | $3.0 to $4.0 / lin ft • Hidden clips |
| PVC | Gap 3/16" (0.1875″) | $4.0 to $5.0 / lin ft • Hidden clips |
| Exotic Hardwood (Ipe) | Gap 1/8" (0.125″) | $6 to $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 to 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.
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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