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.
Inputs
Deck dimensions
Framing
Railing
Stairs
Project cut list
14×16 ft · composite decking · pt-2x8 @ 16″ OC · composite-pvc railing · single
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 |
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
How to use the cut list calculator in 5 steps.
- 1
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.
- 2
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.
- 3
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.
- 4
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.
- 5
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
How DeckMath calculates this — IRC 2021 sources.
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).
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).
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.
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).
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.
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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People also ask
Cut list questions, answered.
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.
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.
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.
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.
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.
±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.
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.
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.
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.
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.
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