What's a deck cut list?

A cut list is the comprehensive lumber order for your deck project — every board, every length, every count. It covers: framing (joists, beams, ledger, rim joists, posts), decking (board count with stock-length math), railing (rails, balusters, posts OR kit pieces by LF), stairs (stringers, treads, risers). Output is a shopping list you bring to the lumber yard. Pros use cut lists to nail accurate bids; DIYers use them to avoid 3-4 trips back to the store.

How do I calculate how many joists I need?

Joist count = ceil(deck width in inches / spacing in inches) + 1. Add 1 because joists start at zero. For 16 ft (192 in) deck @ 16 OC = 12 + 1 = 13 joists. @ 12 OC = 16 + 1 = 17 joists. Plus 2 rim joists (front + back, spanning deck width) and 2 end joists (one of which is replaced by the ledger if attached to house). Total framing pieces typically 17-20 for a 16×14 deck.

What size joists do I need for my deck?

Depends on span + spacing + decking material + species. IRC R507.6 typical: 2×8 PT @ 16 OC spans 12 ft. 2×10 @ 16 OC spans 16 ft. 2×12 @ 16 OC spans 20 ft. Tighter spacing (12 OC) gains ~10% span. Wider spacing (24 OC) loses ~15% span. Use the Joist Span Calculator on this site to get exact spans for your design. The Cut List calc takes joist size as an input — it doesn't compute span tables.

How many decking boards do I need?

Row count = ceil(deck width / (board face width + gap)). Per-row count = ceil(deck span / stock board length). For a 16×14 ft deck with composite 5.5″ + 3/16″ gap and 16 ft stock boards: width 192 in / 5.6875 = 33.7 → 34 rows × 1 board per row (span = stock length) = 34 boards. Same deck with 12 ft stock: 34 rows × 2 boards per row (splice required) = 68 boards. The Cut List calc surfaces this automatically.

Does the cut list include hardware?

No — this calc covers lumber only. Hardware (joist hangers, ledger bolts, structural screws, post bases, hold-downs) is computed by other calcs on this site: Joist Hanger Calculator, Ledger Bolt Calculator, Deck Hardware Calculator. Typical hardware cost adds 10-15% on top of lumber cost. Composite + PVC also need hidden fasteners or color-matched screws — separate item not in this calc.

How accurate is the estimated cost?

±10-20% accurate at the default $/lf prices, which reflect Home Depot/Lowes 2026-Q1 retail. Real-world variance from: regional pricing (NW vs SE varies 25%), lumber price volatility (PT swings 15% seasonally), bulk discounts (5-10% on orders > $2K), and pro-account pricing. Adjust the $/lf input to match your local quote for accurate estimate. The board COUNT is exact; the cost is approximate.

What's the difference between stock length and piece length?

Piece length = the dimension your project needs (e.g., 14 ft joist). Stock length = the standard length you BUY from the lumber yard (8/10/12/14/16/20 ft). For a 14 ft joist: buy 14 ft stock = 1 piece per board (zero waste). For a 13 ft piece: buy 14 ft stock = 1 ft waste per board. The calc picks the smallest stock length that's ≥ piece length to minimize waste. Composite/PVC limited to 12/16/20 ft stock.

How much waste should I budget?

10-12% standard for pros, 12-15% for DIY. The waste % in the calc adds to the estimated cost (not the lumber count — that's already optimized). Reasons for waste: angle cuts, mistakes, board crown forcing re-cuts, splits in delivered lumber, picture-frame border + field cuts. Add 3-5% MORE for diagonal/herringbone patterns. Add 5% for first-time DIYers.

How many stair stringers do I need?

2 stringers for stair width up to 36″ (outer rails). 3 stringers for stair width 36-48″ (outer + center). 4 stringers for > 48″ wide. Stringer length depends on rise + run: hypotenuse of (rise² + run²) ÷ 12 + 1 ft for top connection. For a 42″ rise with 6 risers @ 7″ + 5 treads @ 10″ = stringer length = √(42² + 50²) / 12 + 1 = 6.4 ft. Buy 8 ft 2×12 stock.

Can this calc handle multi-level decks?

Single level only. For multi-level decks (a primary deck + a secondary platform), run the calc TWICE — once per level — and sum the results. The framing for the secondary platform is independent from the primary (assuming they're not bonded). Stairs between levels count once if they share stringers. This calculator targets the most common single-level case which covers ~85% of home deck projects.

Full project lumber order · Framing + decking + railing + stairs · IRC-aware

Deck Cut List Calculator

Generate a complete project lumber order — every framing, decking, railing, and stair piece needed for your deck. Computes: joists at chosen OC (12/16/24″), 2 rim joists (deck width) + 2 end joists (span), 2-ply beams at chosen support count, 4×4 PT support posts at chosen height + count, decking boards with row count + splice math, railing system (wood with 2×4 rails + 2×2 balusters at IRC 4″ sphere spacing OR composite/PVC/aluminum/cable kit), stair stringers (2 or 3 per flight based on width) + stair treads. Surfaces stock board count to buy (e.g., 30 × 16ft 2×8 joists, 67 × 16ft composite boards), grand total linear feet, waste %, and estimated material cost. IRC-aware: warns on joist spacing too wide for composite, stair riser height > 7.75″, missing guard railing > 30″ above grade.

Full cut listStock board count5 decking materialsIRC-aware warnings4 railing systemsStairs includedFree forever

Every piece·Joists / beams / boards / railing / stairs

Stock count·Boards to buy at lumber yard

Est. cost·Material total with waste

IRC-aware·Auto-warns on code violations

Inputs

Deck dimensions

Spanboard run

Widthrows dir

Decking materialsurface

Face widthboard

Board lengthstock

Framing

Joist sizejoist

Joist spacingOC inches

Beam sizebeam

Beamsea

Posts4×4

Post htgrade→top

Railing

RailingLF

Baluster OC4 IRC

Stairs

Total riseinches

Widthinches

Waste %cuts + mistakes

Project cut list

14×16 ft · composite decking · pt-2x8 @ 16″ OC · composite-pvc railing · single

Total boards

Total LF

959.9

Est. cost

$5,480

Waste

10%

Decking

Item	Piece	Count	Stock	Boards to buy
Composite 5/4×6 34 rows × 1 per row	16 ft	34	16 ft	34

Framing

Item	Piece	Count	Stock	Boards to buy
PT 2×8 joist @ 16″ OC	14 ft	13	14 ft	13
PT 2×8 rim joist Front + back	16 ft	2	16 ft	2
PT 2×8 end joist Left + right (or ledger one side)	14 ft	2	14 ft	2
PT 2×10 beam (2-ply) 2 beams × 2 plies each	16 ft	4	16 ft	4
PT 4×4 post	8 ft	4	8 ft	4

Railing

Item	Piece	Count	Stock	Boards to buy
Composite/PVC railing kit Sold as posts + rails + infill kit per LF	50 ft	1	50 ft	10

Stairs

Item	Piece	Count	Stock	Boards to buy
PT 2×12 stair stringer 2 per flight × 1 flight	6.4 ft	2	8 ft	2
Composite 5/4×6 stair tread 5 treads × 1 flight	3 ft	5	12 ft	2

Category totals

Category	Linear ft	Boards
Decking	544	34
Framing	338	25
Railing	50	10
Stairs	27.9	4
GRAND TOTAL	959.9	73

Estimated material cost (10-20% accuracy):$5,480

96 ft waste included (10%). Pricing varies by region — adjust your local quote. Hardware (joist hangers, ledger bolts, hidden fasteners, structural screws) NOT included — adds 10-15% on top.

Recommendations

▸ Stair total rise 42″ might need a landing — IRC R311.7.3 requires landing every 12 ft of vertical rise. For decks > 50″ above grade, consider 2-flights mode with a landing.
▸ Estimated material cost $5,480 (10% waste included). Composite is ~2.5× the cost of PT lumber for the same scope — verify your budget before ordering.

IRC references

• IRC 2021 R507.6 — Joist span limits depend on size + spacing + species
• IRC 2021 R507.5 — Beam span limits (use Beam Span Calculator on this site)
• IRC 2021 R311.7.5.1 — Stair max riser 7.75″, min tread 10″
• IRC 2021 R311.7.3 — Landing required every 12 ft vertical rise
• IRC 2021 R312.1.1 — Guard required when deck > 30″ above grade

How to use

Three steps. Permit-ready output.

Enter deck dimensions + decking material

Deck SPAN = the dimension your boards lay across (typically your deck length). Deck WIDTH = perpendicular. 5 decking materials: PT, cedar, composite, PVC, IPE. Each has documented retail $/lf and available stock lengths. Composite forces 16″ OC joist spacing max per most manufacturer warranty.

Pick framing sizes + joist spacing

Joist size: 2×8 (spans to 12 ft @ 16 OC), 2×10 (to 16 ft), 2×12 (to 20 ft). Use the Joist Span Calculator on this site if unsure. Joist spacing: 12″ OC (heaviest), 16″ OC (most common), 24″ OC (PT only — composite + IPE require 16″ OC max). Beam size matches joist or one size up.

Post count + height + railing system

Posts: typically 4 (corner-only) for decks under 16×16 ft, more for larger. Height = grade to deck-top height. 4 railing systems supported: wood (auto-computes 2×4 rails + 2×2 balusters at chosen OC), composite/PVC kit (LF-based), aluminum kit, cable. Wood mode generates exact baluster + railing-post counts.

Stair scenario + dimensions

No stairs (free-standing deck or ground-level deck) / single flight / two flights (with landing for tall decks). Stair total rise (in inches) drives # of risers (rise / 7.5″). Width drives stringer count (2 for ≤36″, 3 for >36″). Calculator outputs stringers + treads in your chosen decking material.

Read cut list + warnings

Result panel groups by category (Framing / Decking / Railing / Stairs) with stock board count for each item. Grand totals show total linear feet, waste, estimated cost. Warnings: joist spacing too wide for composite, stair riser height violation, missing guard railing > 30″. Use the output as a shopping list at the lumber yard.

How we calculate

The math, fully transparent.

The Cut List Calculator generates a full project lumber order — every framing, decking, railing, and stair piece needed for your deck. Computes: joists at chosen OC (12/16/24″), 2 rim joists (deck width) + 2 end joists (span), 2-ply beams at chosen support count, 4×4 PT support posts at chosen height + count, decking boards with row count + splice math, railing system (wood with 2×4 rails + 2×2 balusters at IRC 4″ sphere spacing OR composite/PVC/aluminum/cable kit), stair stringers (2 or 3 per flight based on width) + stair treads. Surfaces stock board count to buy (e.g., 30 × 16ft 2×8 joists, 67 × 16ft composite boards), grand total linear feet, waste %, and estimated material cost. IRC-aware: warns on joist spacing too wide for composite, stair riser height > 7.75″, missing guard railing > 30″ above grade.

IRC references

IRC 2021 R507.6 — Joist span limits depend on size + spacing + species
IRC 2021 R507.5 — Beam span limits (use Beam Span Calculator on this site)
IRC 2021 R311.7.5.1 — Stair max riser 7.75″, min tread 10″
IRC 2021 R311.7.3 — Landing required every 12 ft vertical rise
IRC 2021 R312.1.1 — Guard required when deck > 30″ above grade

2026-Q1 retail pricing — Home Depot / Lowe's / regional lumber yards. PT 2×8 $2.45/lf, 2×10 $3.20/lf, 2×12 $4.10/lf. PT 4×4 post $3.40/lf. Decking: PT $2.10/lf, cedar $3.80/lf, composite $5.20/lf, PVC $6.50/lf, IPE $6.20/lf. Stair stringer 2×12 $4.50/lf. Estimated cost accuracy ±10-20% (regional variance + bulk discounts not modeled).

Decking board count

boardsNeeded = ceil(width_in / (face_width + 0.1875)) × ceil(span / stock_length)

Row count = deck width inches / (board face + 3/16″ gap), rounded up. Per-row boards = ceil(span / max stock length available for material). For 16 ft span with 12 ft composite stock = 2 boards per row (splices required). For 16 ft span with 16 ft composite stock = 1 board per row (no splices).

Joist count

joistCount = ceil(deck_width_in / spacing_in) + 1

Plus 1 because joists start at zero. Example: 16 ft (192 in) deck @ 16 OC = 12 + 1 = 13 joists. @ 12 OC = 16 + 1 = 17 joists. @ 24 OC = 8 + 1 = 9 joists. Tighter spacing significantly increases joist count + cost.

Stair risers + treads

riserCount = ceil(totalRise / 7.5); treadCount = riserCount - 1; stringerLength = sqrt(rise² + run²) / 12 + 1ft

Risers spaced at ~7-7.75″ each (IRC R311.7.5.1 max). Treads = risers - 1 because top step is the deck surface. Stringer length via Pythagorean: hypotenuse of rise + run + 1 ft for top connection. 36-in stair width = 2 stringers (outer); over 36″ = 3 stringers (outer + center).

Stock board count

stockBoards = ceil(pieceCount / floor(stockLength / pieceLength))

How many stock boards to BUY to get all pieces. Example: 13 joists × 14 ft each needs 13 × 14 ft stock (no shared cuts). But 26 × 3-ft balusters could come from 16ft 2×2 stock at 5 balusters per board → ceil(26/5) = 6 stock boards instead of 26. Optimizes shopping list.

Estimated cost

cost = Σ(stockBoards × stockLength × pricePerLf) × (1 + wastePct/100)

Sum across all items: stock boards × stock length × $/lf for that material. Then apply waste contingency 10-15%. Pricing defaults: PT $2.10/lf, cedar $3.80/lf, composite $5.20/lf, PVC $6.50/lf, IPE $6.20/lf, framing 2×8 $2.45/lf, 2×10 $3.20/lf, 2×12 $4.10/lf. Adjust user $/lf input to match your local pricing.

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Frequently asked

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Deck Material Calculator

Calculate exact decking boards, joists, beams, posts, footings, and fasteners for your deck — IRC 2021 compliant.

Decking Length Calculator

Board-length mix optimizer. 8-20 ft stock lengths × 5 materials. Strategy comparison: single-length vs mixed-length to minimize waste. Pattern waste preset for diagonal/herringbone/picture-frame.

Joist Span Calculator

Maximum joist span for any size, species, and spacing — directly from IRC 2021 R507.6 tables.

Deck Beam Span Calculator

Maximum beam span (post-to-post) by size, ply, species, and tributary load — straight from IRC R507.5 / DCA-6.

Deck Cut List Calculator

Inputs

Decking

Framing

Railing

Stairs

Category totals

Recommendations

IRC references

Three steps. Permit-ready output.

Enter deck dimensions + decking material

Pick framing sizes + joist spacing

Post count + height + railing system

Stair scenario + dimensions

Read cut list + warnings

The math, fully transparent.

IRC references

Don’t lose this estimate.

Questions, answered.

One line. Any site. Free.

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