Joist lines
Divide deck length by maximum joist spacing and include both ends.
Decks & carpentry
Deck material calculator
Estimate a rectangular deck framing layout: joists, side rim or ledger lumber, beam length, support posts, and footing count.
Your material estimate
Joists to plan for
15joists
Includes 10% overage and purchase-unit rounding where applicable.
- Deck area
- 192 sq ft
- Beam rows
- 2 rows
- Support posts
- 6 posts
Example estimate: default sample values are shown. Update the measurements and select Calculate before using or copying this list.
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Shopping list
- Joists spanning the deck widthLayout count plus 10% lumber allowance.15 pieces
- Side rim / ledger framingTwo deck-length sides; convert to available stock lengths.36 linear ft
- Beam material2 beam rows plus 10% lumber allowance.36 linear ft
- Support posts3 posts per beam row at the entered maximum spacing.6 posts
- Post footingsOne footing per estimated support post; size and concrete are not inferred.6 footings
Calculation assumptions
- Joists span the entered deck width and are spaced along the deck length, including both end joist lines.
- Beams run parallel to deck length; post spacing is a maximum planning interval along each beam.
- The 10% allowance applies to joist pieces and linear rim/beam lumber, not structural post count.
- Member sizes, spans, connections, footings, guards, loads, and permits require local code and structural verification.
Framing layout
How deck framing material is estimated
Beams and posts
Multiply beam rows by deck length, then place posts at the entered maximum interval.
Lumber allowance
Add waste to joist pieces and linear beam/rim material before purchase rounding.
Measurement guidance
A quantity layout is not a deck design
Measure the finished rectangular deck edges and confirm which direction the joists run. Enter beam rows and post spacing from the approved framing plan rather than treating the defaults as recommendations.
Joist and beam size, allowable span, species, grade, connections, ledger attachment, lateral load, footings, guards, and permits must follow local code and a suitable design.