Deck Framing Calculator
Every other framing calculator gives you one number. This one gives you the whole frame. Put in the deck size, joist spacing and height and it returns the joist count and lengths, the rim and end joists, how many plies the beam needs, the post and footing count, rows of blocking, and the hanger and hardware counts you take to the counter.
Recommended products for this project
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Outdoor Solid Composite Decking Boards 96"x5.43"x1", Polymer Composite Decking for All Weather Use,Poolside,Backyard,Patio(6 Pcs,Redwood and Maple,21.72sqft)
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Swanson Tool Co PL001M Magnetic Composite Post Level, Yellow, Includes Elastic Loop for Hands-Free Work and 3 Vials for Easy Plumb and Level Reads
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Ready Seal Exterior Wood Stain | Semi-Transparent Oil-Based Formula | Professional Grade Stain and Sealer in One | Ideal for Decks, Fences, Pergolas, Wood Siding & More | 5 Gallon | Natural Cedar
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SUNVIE All-in-One Low Voltage Deck Lights Kit, 8 Pack 5W Low Voltage Landscape Lighting with 60W Transformer 100FT Wire and Connectors, 3000K 12-24V AC/DC LED Deck Step Lights for Fence Post Patio
View on AmazonGet the Smart Decking Calculator app
Estimate decks on the go, save projects, and share with contractors.
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Frequently asked questions
- How many joists do I need for a deck?
- Divide the deck length in inches by the spacing and add one for the closing joist. A 16 ft deck at 16 inches on centre is 192 divided by 16, which is 12, plus one — 13 joists. At 12 inches on centre the same deck needs 17. The extra joists at tighter spacing are why composite decking costs more to frame as well as to buy.
- How far apart should deck posts be?
- Eight feet is the practical maximum along a beam for ordinary residential framing, and many builders use six. The real limit comes from the beam: a doubled 2x10 carrying a 12 ft deck depth will not reach 8 ft between posts in every species. Closer posts mean more footings but a smaller beam, and that trade is usually cheaper.
- Do I need blocking between deck joists?
- Codes generally require blocking or bridging when joists span more than a certain distance, and it is good practice regardless. Blocking stops the joists rolling under load, stiffens the whole frame noticeably underfoot, and gives you something to fasten to under a picture-frame border or a diagonal pattern. One row per 8 ft of span is the usual rule.
- Should my deck be freestanding or attached to the house?
- Attached is cheaper and uses less lumber, but the ledger connection is the deck's biggest structural risk and some wall types — brick veneer, stucco over foam, a cantilevered floor — cannot carry one at all. Freestanding needs a second beam and another row of footings, but it never loads the house, never leaks into the band joist, and often skips the hardest part of the inspection.
