How do I calculate how much Trex decking I need?

Divide the deck depth (across the boards) by 5.69 inches — a 5.5-inch board plus the 3/16-inch gap — to get the number of rows. Multiply by how many boards each row needs (row length ÷ 12, 16 or 20 ft, reusing offcuts), then add about 5% for miscuts. A 20 × 12 ft deck is 26 rows of 20-ft boards: 26 boards, or 28 to order.

How many Trex boards do I need for a 20 × 12 deck?

28 twenty-foot boards (560 linear ft) with the boards running along the 20-ft side: 26 rows plus 5% extra. With 16-ft boards it is 33 boards before the extra, because each row needs a 16-ft board plus a 4-ft piece. In Trex Enhance Naturals the boards cost about $2,212.

How many Trex boards for a 12 × 12 deck?

28 twelve-foot boards (26 rows plus 5%), covering 144 sq ft. Materials in Trex Enhance Naturals come to about $1,453 including 3 boxes of hidden clips.

How many 16-foot Trex boards do I need for a 16 × 12 deck?

28 sixteen-foot boards: 12 ft = 144 in ÷ 5.69 in = 26 rows, one board per row, plus 5% extra. The last row is ripped to about 1.8 in unless you make the deck slightly shallower or deeper.

How many square feet does a Trex board cover?

With the 3/16-inch minimum gap, a 12-ft board covers 5.69 sq ft, a 16-ft board 7.58 sq ft and a 20-ft board 9.48 sq ft. With a 1/4-inch gap: 5.75, 7.67 and 9.58 sq ft.

How do I convert Trex linear feet to square feet?

One square foot of deck takes 2.11 linear feet of 5.5-inch board at a 3/16-inch gap. Square feet = linear feet ÷ 2.11; linear feet = square feet × 2.11. For example, 180 boards of 16 ft (2,880 linear ft) cover about 1,365 sq ft before waste.

How much does Trex decking cost per square foot?

Boards alone run about $6.96 per sq ft for Enhance Basics, $8.33 for Enhance Naturals, $9.49 for Select and $11.39 for Transcend at 2026 average prices. A complete new deck, professionally built with framing, typically costs $25–$65 per sq ft depending on the line (HomeGuide reports up to $70).

How much does a Trex board cost?

A 16-ft board costs roughly $53 (Enhance Basics), $63 (Enhance Naturals), $72 (Select) and $86 (Transcend) at 2026 average retail prices of $3.30–$5.40 per linear foot. Store prices and sales vary, so enter your dealer’s price per linear foot in the calculator.

How much does a 10 × 20 Trex deck cost?

200 sq ft: about $5,000–$7,000 in Enhance Basics, $6,000–$10,000 in Select and $9,000–$13,000 in Transcend for a new, professionally built deck with framing, before railings and stairs. The decking boards alone are roughly $1,400–$2,300.

How much does a 20 × 20 or 25 × 25 Trex deck cost?

A 20 × 20 (400 sq ft) new Trex deck typically runs $10,000–$26,000 installed. A 25 × 25 (625 sq ft) runs $15,625–$40,625. DIY decking materials are about $3,970 and $6,113 in Trex Enhance Naturals.

What is the labor cost to install a Trex deck?

Labor for installing composite decking typically runs $8–$22 per sq ft (Angi), and $15–$35 per sq ft when it includes framing, stairs and railings. On a 240 sq ft deck that is $1,920–$5,280 to lay new boards on an existing frame.

How much does it cost to replace a deck floor with Trex?

If the existing frame is sound and joists are 16 inches on center, you pay for boards, clips and labor only. A 10 × 10 resurface comes to about $1,832–$3,232 in Trex Enhance Naturals; a 20 × 12 about $4,342–$7,702. Joists at 24 inches need a new joist added between each pair.

How much Trex do I need for a 23 × 18 deck?

48 twenty-foot boards (960 linear ft) with boards running along the 23-ft side: 38 rows, each a 20-ft board plus a 3-ft piece. That covers 414 sq ft; clips are 8 boxes.

What are Trex board dimensions?

Trex Enhance, Transcend and Signature 1×6 boards are actually 0.94 in thick × 5.5 in wide; Select is 0.82 in × 5.5 in. Lengths are 12, 16 and 20 ft (availability varies by line and color). Fascia is 0.56 in × 7.25 in (1×8) or 11.375 in (1×12), 12 ft long.

What joist spacing does Trex require?

Trex 1×6 decking needs joists no more than 16 inches on center for residential decks, 12 inches on center for diagonal installs, and every board must span at least three joists. If you are resurfacing a wood deck with joists 24 inches on center, add a joist between each existing pair.

How do I calculate Trex stairs?

Divide the total rise by 7.75 inches (maximum riser) and round up for the number of risers; treads = risers − 1. Each tread is two 5.5-inch boards (11.25 in deep with the gap). Stringers go 9 inches on center for Enhance and 12 inches for Select and Transcend, with at least four. A 30-inch rise, 4 ft wide, is 4 risers, 3 treads, 2 twelve-foot tread boards and 7 stringers in Enhance.

What is Trex RainEscape and how much do I need?

Trex RainEscape is an over-the-joist drainage system: 20-mil troughs between the joists slope water at 1/4 in per foot to downspouts at the outer rim and into a gutter, keeping the space under an elevated deck dry. You need one trough and one downspout per joist bay. A 20-ft-wide deck with 12-ft joists at 16 inches on center takes about 15 twelve-foot troughs, 15 downspouts and 5 rolls of 4-inch butyl tape.

How many hidden fasteners do I need for Trex?

One Trex Hideaway clip per joist per row. A box of 90 covers about 50 sq ft at 16 inches on center, so a 240 sq ft deck needs about 416 clips — 5 boxes. Add start clips for the first row and plan face screws or butt-joint clips where boards meet.

How many screws do I need for Trex decking?

Trex requires two screws per joist on every board, which is about 316 screws per 100 sq ft at 16 inches on center. A 20 × 12 deck face-screwed needs about 832 screws.

How much does Trex decking weigh?

Per linear foot: Enhance 1.9 lb, Select 2.2 lb and Transcend 2.4 lb (Trex cut sheets). A 16-ft board weighs about 30, 35 and 38 lb respectively. Ninety 16-ft Enhance boards weigh about 2,736 lb — check your truck or trailer rating.

How much does Trex expand with temperature?

Trex lists a coefficient of thermal expansion of 1.9 × 10⁻⁵ in/in/°F. A 70-inch piece grows about 0.04 in over a 30°F swing; a 20-ft board about 0.23 in over 50°F. That is why Trex specifies 1/8-inch end gaps above 40°F and 3/16-inch below.

What gap should I leave between Trex boards?

At least 3/16 inch side to side (Trex hidden clips set this automatically), 3/8 inch in heavily wooded areas, and never more than 1/2 inch. End to end, leave 1/8 inch if installing above 40°F and 3/16 inch below 40°F.

What waste factor should I use for Trex?

This calculator counts offcuts exactly, so 5% extra is enough for miscuts and damaged boards on a rectangle. Use 10% for L-shapes, picture framing or breaker boards, and 15% or more for diagonal decking — the 20 × 12 diagonal estimate is 30 boards versus 28 straight.

What is the difference between Trex Enhance, Select and Transcend?

Enhance (Basics and Naturals) is the budget line with a scalloped underside, so its stair stringers must be 9 inches on center. Select is a solid 0.82-inch board. Transcend is the premium solid board with the deepest grain and the most colors. Prices run about $3.30, $4.50 and $5.40 per linear foot.

How much does Trex railing and stairs cost?

Trex Select railing runs about $35–$55 per linear foot installed; a 6-ft Select Classic rail and baluster kit lists at about $156 before posts. Composite stairs run about $100–$200 per step installed. Enter railing feet and steps in the calculator to add them.

How does this Trex calculator work?

It lays out real 5.5-inch rows across the deck depth, tests 12-, 16- and 20-ft boards against your row length (reusing offcuts, with every piece spanning at least three joists), picks the length with the least waste, adds your miscut allowance, then counts joists, hidden clips, screws and weight. Cost uses 2026 average prices per linear foot (or yours), plus published installed ranges for pro projects.

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Composite decking · Trex install-guide rules · 2026 prices · updated October 2, 2026

Trex Calculator: How Many Trex Boards You Need and What They Cost

Quick answer

Each 5.5-inch Trex board plus its 3/16-inch gap covers 5.69 inches of deck, so you need 2.11 linear feet per square foot — a 16-ft board covers 7.58 sq ft. A 20 × 12 ft deck is 26 rows: 28 twenty-foot boards with 5% extra, 5 boxes of hidden clips and 16 joists at 16 inches on center. Boards cost about $6.96–$11.39 per sq ft (Enhance Basics to Transcend); a new, professionally built Trex deck typically runs $25–$65 per sq ft.

Enter your deck size to get the exact board count for 12-, 16- and 20-ft Trex boards, hidden clips, joists, weight and cost for Enhance, Select or Transcend — DIY, resurfacing or a new pro-built deck. Separate tabs size Trex stairs and estimate Trex RainEscape under-deck drainage.

Row-by-row board count with the best board length
Clips, screws, joists and order weight
Cost by Trex line, DIY or pro, with railing and stairs
Trex stairs and RainEscape material estimates

Last updated October 2, 2026. Free, no sign-up. Guides: how many Trex boards · Trex cost per square foot

Trex Decking Calculator

Boards, clips, joists and cost for any deck size — plus Trex stairs and a RainEscape under-deck drainage estimator.

Deck length along the boards(ft)

Usually the side parallel to the house

Deck depth across the boards(ft)

Joist length, house to outer rim

Trex line

Board length

Pattern

Side gap

Extra for miscuts(%)

Offcuts are already counted

Your price per linear ft($)

Blank = 2026 average

Railing(linear ft)

Stair steps(count)

Project

Boards to order

28 × 20 ft

560 linear ft · 240 sq ft deck

Decking materials

$2,422

$2,212 boards + $210 clips · $10.09/sq ft

DIY decking total

$2,422

$10.09 per sq ft

Rows of boards

9.48 sq ft per 20-ft board

Joists

16 @ 16" OC

12 ft long

Hidden clips

5 boxes

≈416 clips, or 832 screws if face-screwed

Order weight

1,064 lb

1.9 lb per linear ft

Board length	Boards (before extra)	Linear ft	Offcut	Board cost
12 ft	52	624	16.7%	$2,465
16 ft	33	528	1.5%	$2,086
20 ft	26	520	0.0%	$2,054

Area: 20 × 12 ft = 240 sq ft.
Rows: 12 ft = 144 in ÷ (5.5 in board + 3/16" gap) = 26 rows (last row ripped to 1.8 in).
Each row is 20 ft long; with 20-ft boards that is 26 boards (0% offcut).
Add 5% for miscuts and damage: order 28 boards (560 linear ft).
Joists at 16" on center: 16 joists, 12 ft long. Hidden clips: about 416 (5 boxes of 90).

The last row is only 1.8 in wide. Make the deck 1.8 in shallower or 3.9 in deeper to finish on a full board, or rip the first and last rows evenly.

Prices are 2026 national averages ($79 per 20-ft Trex Enhance Naturals board at $3.95/lin ft). Enter your dealer’s price for an exact figure. Fascia, framing hardware, footings, permits and tax are not included unless you choose a pro-installed project.

How the Trex board count is calculated

A Trex calculator works out how many composite deck boards, hidden clips and joists a deck needs, and what they cost. Trex boards are 5.5 inches wide and come in 12-, 16- and 20-foot lengths; with the minimum 3/16-inch gap each board takes 5.69 inches of deck, so you need 2.11 linear feet of board per square foot. Rows = deck depth ÷ 5.69 in; boards per row depend on how the row length divides into 12-, 16- or 20-foot boards.

rows = depth (in) ÷ (5.5 + gap) · boards = rows × boards per row (offcuts reused, each piece ≥ 3 joists) · order = boards × (1 + extra %)
linear ft per sq ft = 12 ÷ (5.5 + gap) = 2.11 · clips ≈ rows × joists · joists = length (in) ÷ 16 + 1

Example — 20 × 12 ft, boards along the 20-ft side: 144 in ÷ 5.6875 in = 26 rows (the last one ripped to 1.8 in). 20-ft boards fit each row exactly, so 26 boards; 16-ft boards would need 33 and 12-ft boards 52. Adding 5% gives 28 boards (560 linear ft). 16 joists × 26 rows ≈ 416 clips = 5 boxes. In Trex Enhance Naturals that is about $2,422, or $10.09 per sq ft.

Why the old “deck length ÷ joist spacing” shortcut is wrong: it counts joists, not boards. The deck depth decides how many rows you need, and the row length decides which board length wastes least.

How many Trex boards for common deck sizes

Boards run along the first dimension, 3/16-inch gap, best board length, 5% extra. Materials include boards and hidden clips at 2026 average prices.

Deck	Sq ft	Rows	Boards to order	Linear ft	Clip boxes	Trex Enhance Naturals	Transcend
10 × 8 ft	80	17	10 × 20 ft	200	2	$874	$1,164
10 × 10 ft	100	22	12 × 20 ft	240	2	$1,032	$1,380
12 × 10 ft	120	22	24 × 12 ft	288	3	$1,264	$1,681
12 × 12 ft	144	26	28 × 12 ft	336	3	$1,453	$1,940
16 × 12 ft	192	26	28 × 16 ft	448	4	$1,938	$2,587
16 × 16 ft	256	34	36 × 16 ft	576	5	$2,485	$3,320
20 × 12 ft	240	26	28 × 20 ft	560	5	$2,422	$3,234
20 × 16 ft	320	34	36 × 20 ft	720	7	$3,138	$4,182
20 × 20 ft	400	43	46 × 20 ft	920	8	$3,970	$5,304
24 × 12 ft	288	26	41 × 16 ft	656	6	$2,843	$3,794
24 × 16 ft	384	34	54 × 16 ft	864	8	$3,749	$5,002
25 × 25 ft	625	53	71 × 20 ft	1420	12	$6,113	$8,172
30 × 16 ft	480	34	54 × 20 ft	1080	9	$4,644	$6,210
40 × 20 ft	800	43	91 × 20 ft	1820	15	$7,819	$10,458

Trex coverage per board

Square feet each board covers, and boards per 100 and 1,000 sq ft before waste.

Board	Covers (3/16" gap)	Covers (1/4" gap)	Per 100 sq ft	Per 1,000 sq ft
12 ft	5.69 sq ft	5.75 sq ft	18	176
16 ft	7.58 sq ft	7.67 sq ft	14	132
20 ft	9.48 sq ft	9.58 sq ft	11	106

Trex installation rules

Item	Requirement	Note
Board size	Enhance, Transcend, Signature: 0.94" × 5.5"; Select: 0.82" × 5.5"	12, 16 or 20 ft lengths
Side (width-to-width) gap	3/16" minimum; 3/8" in heavily wooded areas	Never more than 1/2"
End-to-end gap	1/8" above 40°F, 3/16" below 40°F	Butt joints must land on framing
Joist spacing	16" on center (residential); 12" for diagonal decking	Every board must span at least 3 joists
Overhang	Board ends: 3/4" maximum past the rim	Fascia goes under the board ends
Fastening	Hidden clips: 1 per joist per row; screws: 2 per joist	1 box of 90 clips ≈ 50 sq ft at 16" OC
Stair stringers	Enhance: 9" on center; Select and Transcend: 12"	At least 4 stringers; treads gapped 1/4"–3/8"
Live load	100 psf at 16" on center for 1×6 boards	IRC requires 40 psf for decks

Trex Enhance vs Select vs Transcend: price, weight and specs

Line	Per lin ft	16-ft board	Boards per sq ft	New deck installed	Size	Weight	Stair stringers
Trex Enhance Basics	$3.30	$53	$6.96	$25–$35	0.94" × 5.5"	1.9 lb (30 lb per 16 ft)	9"
Trex Enhance Naturals	$3.95	$63	$8.33	$30–$40	0.94" × 5.5"	1.9 lb (30 lb per 16 ft)	9"
Trex Select	$4.50	$72	$9.49	$30–$50	0.82" × 5.5"	2.2 lb (35 lb per 16 ft)	12"
Trex Transcend	$5.40	$86	$11.39	$45–$65	0.94" × 5.5"	2.4 lb (38 lb per 16 ft)	12"

Prices are 2026 national retail averages; your dealer, color and board length change them. Installed ranges include framing and labor but not railings, stairs or permits.

Trex deck cost by size (new deck, professionally installed)

Deck	Enhance Basics	Enhance Naturals	Select	Transcend
10 × 10 ft (100 sq ft)	$2,500–$3,500	$3,000–$4,000	$3,000–$5,000	$4,500–$6,500
12 × 10 ft (120 sq ft)	$3,000–$4,200	$3,600–$4,800	$3,600–$6,000	$5,400–$7,800
12 × 12 ft (144 sq ft)	$3,600–$5,040	$4,320–$5,760	$4,320–$7,200	$6,480–$9,360
16 × 12 ft (192 sq ft)	$4,800–$6,720	$5,760–$7,680	$5,760–$9,600	$8,640–$12,480
16 × 16 ft (256 sq ft)	$6,400–$8,960	$7,680–$10,240	$7,680–$12,800	$11,520–$16,640
20 × 12 ft (240 sq ft)	$6,000–$8,400	$7,200–$9,600	$7,200–$12,000	$10,800–$15,600
20 × 16 ft (320 sq ft)	$8,000–$11,200	$9,600–$12,800	$9,600–$16,000	$14,400–$20,800
20 × 20 ft (400 sq ft)	$10,000–$14,000	$12,000–$16,000	$12,000–$20,000	$18,000–$26,000
24 × 12 ft (288 sq ft)	$7,200–$10,080	$8,640–$11,520	$8,640–$14,400	$12,960–$18,720
24 × 16 ft (384 sq ft)	$9,600–$13,440	$11,520–$15,360	$11,520–$19,200	$17,280–$24,960
25 × 25 ft (625 sq ft)	$15,625–$21,875	$18,750–$25,000	$18,750–$31,250	$28,125–$40,625
30 × 16 ft (480 sq ft)	$12,000–$16,800	$14,400–$19,200	$14,400–$24,000	$21,600–$31,200

Add about $35–$55 per linear foot for Trex Select railing and $100–$200 per stair step. Resurfacing an existing frame costs much less: boards and clips plus $8–$22 per sq ft labor.

Trex stair calculator chart

Enhance treads (9-inch stringers), two boards per tread, 7.75-inch maximum riser.

Rise	Risers / treads	Riser	3-ft treads	4-ft treads	Stringers (4 ft)	Run
18"	3 / 2	6.00"	1 × 12 ft	2 × 12 ft	7	1.8 ft
24"	4 / 3	6.00"	2 × 12 ft	2 × 12 ft	7	2.6 ft
30"	4 / 3	7.50"	2 × 12 ft	2 × 12 ft	7	2.6 ft
36"	5 / 4	7.20"	2 × 12 ft	3 × 12 ft	7	3.5 ft
48"	7 / 6	6.86"	3 × 12 ft	4 × 12 ft	7	5.3 ft
60"	8 / 7	7.50"	4 × 12 ft	5 × 12 ft	7	6.1 ft
72"	10 / 9	7.20"	5 × 12 ft	6 × 12 ft	7	7.9 ft
96"	13 / 12	7.38"	6 × 12 ft	8 × 12 ft	7	10.5 ft

Trex RainEscape materials by deck size

Width along the house × joist length, joists 16 inches on center, no posts inside the frame.

Deck	Troughs	Downspouts	Tape rolls	Caulk	Gutter
12 × 10 ft	9 × 12 ft	9	3	1	12 ft
16 × 12 ft	12 × 12 ft	12	4	1	16 ft
20 × 12 ft	15 × 12 ft	15	5	1	20 ft
20 × 16 ft	15 × 16 ft	15	6	1	20 ft
24 × 14 ft	18 × 16 ft	18	7	1	24 ft
30 × 16 ft	23 × 16 ft	23	9	2	30 ft

Trex thermal expansion

Length change at 1.9 × 10⁻⁵ in/in/°F (Trex specification) for different temperature swings.

Board length	30°F swing	50°F swing	80°F swing
70 in	0.040 in	0.067 in	0.106 in
12 ft	0.082 in	0.137 in	0.219 in
16 ft	0.109 in	0.182 in	0.292 in
20 ft	0.137 in	0.228 in	0.365 in

Plan the depth to the board

Size the deck depth in 5.69-inch steps so the last row is a full board, or rip the first and last rows evenly.

Check the existing frame

Resurfacing? Joists must be 16 inches on center (12 for diagonal), flat and sound. Add sister joists where needed.

Order one length

Pick the board length that matches your row length. Butt joints and short offcuts add labor and waste.

Sources and how this calculator was checked

Board sizes, gaps, spans, stair spacing, weights and expansion come from Trex installation guides, cut sheets and specifications; RainEscape quantities from the manufacturer’s component sizes. Prices are 2026 national averages from retailers and cost guides and will differ locally. Every table on this page is generated by the same code as the calculator. Trex, RainEscape and Hideaway are trademarks of Trex Company, Inc.; this independent calculator is not affiliated with Trex. Check local codes and permits.

Trex — 2024 Decking Installation Guide (dimensions, spans, stairs)0.94" × 5.5" boards (Select 0.82"), 12/16/20 ft; joists 16" OC; boards span 3 joists; stair stringers 12" OC (Transcend/Enhance 1×6), treads gapped 1/4"–3/8".
Trex — 2026 Decking Installation Guide3/16" minimum side gap (3/8" wooded, 1/2" max); end gap 1/8" above 40°F, 3/16" below; 3/4" max overhang; two screws per joist; Enhance stair treads 9" OC.
Trex Academy — How to space and install deck joists16" OC for composite decking, 12" for diagonal; add a joist between 24" OC joists when resurfacing; row-count method.
Trex — Enhance, Select and Transcend cut sheetsWeight per lineal foot: Transcend 2.4 lb, Select 2.2 lb, Enhance 1.9 lb; fascia 0.56" × 7.25" and 11.375".
Trex — Transcend decking architectural specificationThermal expansion 1.9 × 10⁻⁵ in/in/°F (ASTM D1037); moisture absorption under 1%.
Trex — Hideaway Universal Hidden FastenersBox of 90 clips covers 50 sq ft at 16" on center.
Trex RainEscape — Installation guideTroughs 19-5/8" × 12 or 16 ft (no splicing); downspouts fit 12" or 16" OC; 4" × 50 ft butyl tape; caulk tube ≈ 25 ft; 1/4" per foot fall, 4" max depth; gutter outlets every 12–14 ft.
Trex RainEscape — Official materials estimatorManufacturer estimator — confirm quantities before ordering.
HomeGuide — Trex decking cost (2026)New Trex deck $45–$70 per sq ft installed including framing; boards alone $5–$15 per sq ft.
Angi — How much does Trex decking cost?Complete Trex deck $20–$62 per sq ft; labor $8–$22 per sq ft ($15–$35 with framing, stairs and railings).
FieldRate — Contractor pricing guide for Trex decking (2026)Installed by line, substructure included: Enhance Basics $25–$35, Naturals $30–$40, Select $30–$50, Transcend $45–$65 per sq ft.
DeckMath — Trex Enhance vs Select vs Transcend (2026)2026-Q1 retail averages: $3.30, $3.95, $4.50 and $5.40 per linear foot.
Trex — Select Classic 6′ × 36″ rail and baluster kitList price about $156 per 6-ft kit (posts sold separately).
ICC — 2021 International Residential Code, Section R311.7 (stairways)Maximum riser 7-3/4", minimum tread 10", minimum width 36"; handrail required with four or more risers.

Building the frame too? Use the deck calculator for joists and footings. Deck builders and lumber yards: we build branded estimators for your website.

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