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Deck material calculator
Enter the deck size in feet and get the lumber list: decking boards by stock length, joists at 16 in on center, beams, posts, footings, stairs, railing and fasteners. Drawn in 3D as you type. Free, no sign-up, and nothing is priced until you add your own rates.
Example lumber list, until you enter your size
| Item | To buy | Rule |
|---|---|---|
| Decking boards | 28 at 16 ft | Rows packed into stock lengths, 5% waste included |
| Joists | 13 at 16 in o.c. | US residential practice (IRC / DCA 6) |
| Beams | 3 (48 ft total) | House, outer edge, and one more when the joist span runs out |
| Posts | 9 | No more than 8 ft apart, one footing each |
| Footings and concrete | 9 and 27 bags | 20 kg post-set bags, one footing at a time |
| Stairs | 3 stringers, 5 treads | Rise and going follow IRC stair limits |
| Railing | 37 ft and 12 posts | Rail at 36 in, posts at the corners and ends |
| Fascia | 40 ft | Around the exposed edges of the frame |
| Joist ties | 26 | Drop beam: one where each joist bears on a beam |
| Structural fixings | 18 | Two at each post-to-beam connection |
| Hidden clips | 377 clips | Counted from the board-to-joist crossings, not estimated |
| Weed membrane | 192 sq ft | Laid under the whole deck before the frame goes down |
The board count already carries 5% for cuts and offcuts. Every rule behind these numbers is written out on the methodology page.
The full list has beams, hangers, footings, stairs, railing and the cut list.
Open the deck designer to change the material, the height, the railing, the stairs and the country, inspect everything on screen and save a summary PDF. The complete pack adds the exact cut list and merchant CSV.
Inspect the full material listFree, no sign-up. Nothing is priced until you add your own rates.
What the numbers follow in the US
- Decking boards
- 5 1/2 in face with a 3/16 in gap, bought in 8, 10, 12, 14 and 16 ft lengths. Rows are packed into those lengths so you order what the yard sells.
- Joists at 16 in on center
- The standard spacing for solid-sawn framing. Most composite boards want 12 in on center, and the count changes with the material you pick.
- Beams and posts
- Posts no more than 8 ft apart, one footing under each. The span warning names the next joist section up when your run is too long.
- Fasteners
- Face screws or hidden clips, joist hangers for every flush connection, plus the concrete for the footings. All counted, not estimated.
Building in Canada, the UK or Ireland? Pick the country in the designer and the spacings, stock lengths and stair rise change with it.
What about the cost of the materials?
Lumber prices move week to week and vary by yard, so no average here would be worth anything. Put in the rate you actually pay per board, per joist, per hanger, per bag of concrete, and the same take-off turns into money you can stand behind.
Common questions
What lumber do I need for a deck?
Decking boards for the surface, 2x joists at 16 in on center, a beam under them, 6x6 posts on footings, joist hangers and fasteners. The calculator counts each of those from the size you enter and shows the rule beside the number.
How many joists for a 16x12 deck?
Joists run across the 12 ft direction at 16 in on center, so it is 16 ft divided by 16 in, rounded up, plus one: 13 joists. Blocking and the rim board are counted separately.
What size joists should I use?
It depends on the span. The calculator flags the span against common US practice (DCA 6 / IRC) and names the next section up when the run is too long for what you picked.
How much does deck material cost?
Only your own supplier prices answer that. Nothing here is priced from a national average. Enter what your yard charges per board, per joist, per bag of concrete, and the total appears next to the quantities.
Is this a structural design?
No. It is a material take-off from your measurements and common US residential practice. Spans, footing depth, frost line and local approval are still your inspector's call.
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