Deck framing layout estimator

Deck Joist Calculator

Estimate deck joist count, on-center layout, blocking pieces, rim-board length, total framing footage, waste, and rough material cost from deck width, joist span, and spacing.

Units

Deck width across joists (ft)Joist span / length (ft)On-center spacing (in)Rim board runs Blocking rows Waste / extras (%)Cost per joist ($)Cost per block ($)

Joists to buy

Joist rows

Linear framing

Rough cost

Joist count is not span design

This calculator counts layout material only. Joist size, species, grade, span, load, beam/post layout, hangers, blocking requirements, fasteners, and local deck code must be verified before building.

Android App

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Deck Board Calculator

Estimate deck board rows and linear footage.

Deck Cost Calculator

Price deck boards, joists, railing, labor, and fasteners.

Deck Railing Posts

Lay out guardrail post spacing before finishing the deck.

View all

Deck joist formula

Joist rows = deck width ÷ on-center spacing + 1

Joists to buy = joist rows × (1 + waste %)

Blocking pieces = blocking rows × spaces between joists

Linear footage = joist rows × joist span + rim boards + blocking length

Sample takeoff

A 12 ft wide deck with 16 ft joists at 16 in on-center, two rim boards, one blocking row, and 10% waste needs about 11 joists and 197.3 linear ft of framing.A 3.6 m wide deck with 4.8 m joists at 400 mm on-center, two rim boards, one blocking row, and 10% waste needs about 11 joists and 58.8 m of framing.

Deck Joist Calculator FAQ

Does this deck joist calculator choose joist size?+

No. It counts joists and blocking. Use span tables, product data, an engineer, or your local code authority to choose joist size, species, grade, and allowable span.No. It counts joists and blocking. Use span tables, product data, an engineer, or your local code authority to choose joist size, species, grade, and allowable span.

How many joists do I need at 16 inches on center?+

Convert the deck width to inches, divide by 16, round up, then add one joist for the starting edge. VibeCalc adds your waste percentage to the buy count.Convert the deck width to inches, divide by 16, round up, then add one joist for the starting edge. VibeCalc adds your waste percentage to the buy count.

Should I add blocking rows?+

Add blocking when required by code, joist depth, deck board layout, bracing plan, or inspection. The calculator multiplies each blocking row by the spaces between joists.Add blocking when required by code, joist depth, deck board layout, bracing plan, or inspection. The calculator multiplies each blocking row by the spaces between joists.