Plan your deck
board by board.
Most deck calculators divide your area by a board size and add 10%. Deckwright lays out every row, puts every seam on a joist, sizes the framing from the building code tables, and hands you a shopping list by length.
Free. No sign-up. Your plan lives in the link.
Calculators
Each one stands alone, and the planner combines them into one list.
Deck Planner
Decking, framing, footings, hardware and concrete in one shopping list, with a plan drawing.
Open →Deck Board Calculator
Boards by stock length with seams placed on joists, plus screws or hidden clips.
Open →Joist Span Calculator
Maximum joist span and cantilever from IRC Table R507.6, and the joist count.
Open →Beam & Post Spacing
Beam size against post spacing from IRC Table R507.5, compared side by side.
Open →Footing Calculator
Footing size from tributary area and soil, plus concrete bags per hole.
Open →Deck Stair Calculator
Risers, treads, stringer length and throat, with a drawing to scale.
Open →Railing & Baluster Calculator
Posts, balusters and rails with every gap kept under the 4-inch sphere rule.
Open →Deck Stain Calculator
Gallons for the deck, railings and stairs, using your product’s label coverage.
Open →Deck Cost Calculator
Budget ranges with named sources, or an itemized cost built from your local prices.
Open →Metric Decking Calculator
m², linear metres and boards by length for UK, Australian and NZ decks.
Open →Deck Span Tables
Every IRC joist, beam, post, footing and ledger table on one printable page.
Open →Area math vs. real boards
Composite decks, 5½″ boards, 12′ and 16′ lengths only, joists 16″ o.c. The area method assumes all 16′ boards plus 10%.
| Deck | Area method | Deckwright | What to actually buy | Linear ft bought |
|---|---|---|---|---|
| 10×12 | 18 boards | 24 boards | 13×16′ + 11×12′ | 340 vs 288 lin ft |
| 12×16 | 28 boards | 41 boards | 41×12′ | 492 vs 448 lin ft |
| 12×20 | 35 boards | 41 boards | 28×16′ + 13×12′ | 604 vs 560 lin ft |
| 14×20 | 41 boards | 48 boards | 33×16′ + 15×12′ | 708 vs 656 lin ft |
| 16×24 | 56 boards | 68 boards | 44×16′ + 24×12′ | 992 vs 896 lin ft |
Sometimes the area method over-buys and sometimes it leaves you short. It can’t tell which, because it never lays out a row. Ours includes 5% spare boards. Read the full waste study across 21 deck sizes →
Board by board
Real stock lengths, seams on joists, staggered rows and reused offcuts. Straight, diagonal and picture-frame layouts.
Code-referenced
Joists, beams, posts, footings, stairs and guards are checked against IRC tables, and every check names its section. Where sources conflict, we take the safer value and say so.
Honest about cost
No invented prices. Enter your store’s prices once and every list prices itself. Published ranges are shown with their source.
Common deck sizes
All sizes →Guides
All guides →How many deck boards do I need?
Why area ÷ board size undercounts, and how to plan boards by stock length.
Read →How to stagger deck boards (with a real cut plan)
Butt-joint rules, common patterns, and a row-by-row cut plan for a 24 ft deck.
Read →Deck joist spacing: 12, 16 or 24 inches?
What the IRC tables allow, what decking manufacturers require, and diagonal layouts.
Read →