Deck calculator: joists, beams, decking and cost
Deck framing is where estimating and structure collide. Joist spacing sets your board count, your hanger count, your fastener count and whether the finish surface feels solid underfoot — so it is worth resolving before you price anything else.
Enter footprint, framing species, spacing and decking type, and the takeoff returns framing members, footings, hangers, boards and fasteners with a span check that flags any joist or beam outside standard span tables. It is a planning aid, not a stamped design; loaded, elevated or roof-covered decks should be reviewed locally.
Estimates only — not a quote.
Open the deck builderIncluded in the takeoff
- Joist, beam, post and footing counts
- Decking board count at your width and gap, with waste
- Hanger, hardware and fastener quantities
- Span check against IRC-style tables
- Stair stringer and railing components
Inputs
- Deck length, width and height above grade
- Framing species and joist spacing
- Decking material, board width and gap
- Stair count and railing style
Common deck sizes, calculated
Quick answers for the sizes people search most. Your yard will differ — enter your own numbers for a plan that fits.
| Size | Joists | Decking boards | Footings | Concrete bags | Est. materials |
|---|---|---|---|---|---|
| 10×10 ft | 9 | 25 | 6 | 30 | $2,118 |
| 12×12 ft | 10 | 29 | 6 | 30 | $2,376 |
| 16×12 ft | 13 | 58 | 6 | 30 | $3,247 |
| 20×16 ft | 32 | 77 | 8 | 40 | $4,562 |
How these numbers work: Assumes an attached pressure-treated deck 3 ft off the ground, joists 16" on center, 12 ft decking boards, railings, 4 stair risers and 10% waste. Board counts round up, so you never come up short on install day. National average prices before your ZIP is applied. Estimates only, never a quote.
Plan it in 5 steps
- 1Fix the footprint
Square the outline and confirm it clears setbacks and any easement. The footprint drives every quantity that follows.
- 2Choose spacing before material
Composite and diagonal patterns often need 12-inch centers. Set spacing first, then price boards.
- 3Run the span check
Confirm your joist and beam spans sit inside the table for your species and size before ordering lumber.
- 4Plan footings for your frost line
Footing depth is local. Look it up for your address; it changes concrete volume noticeably.
- 5Price two decking options
Run the same frame with pressure-treated and composite decking to see the real delta before you decide.
Planning guidance only. Every quantity and price is an estimate — confirm dimensions and local requirements before you buy or build.
Run your own numbers
Enter your dimensions and get a material list, cut list and regional cost estimate in a couple of minutes. No account needed to see the takeoff.
Start estimatingBidding deck builder work for clients?
Contractors and handymen run this deck builder to build the material takeoff, nest the cut list, check permits by ZIP and hand the client a branded proposal — same visit, before the estimate goes cold.
- Takeoff priced to your ZIP in minutes
- Cut list that trims the lumber order
- Branded proposal and invoice PDFs
Material and cost output is an estimate, never a quote. Permit content is guidance to verify with your local building department.
Frequently asked questions
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