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Free deck and patio calculators

Count the lumber, size the joists, beams and pergola members, find the footings, lay out the stairs, and count the pavers or concrete for a patio. Each tool says where its numbers come from, so you can check it.

Ready to design the whole deck?

The calculators answer one question at a time. The 3D deck designer sizes the whole deck with the same tables and checks every part against them.

Open the deck designer

Questions

Anything else? Write to us or read the span tables.

About these tools

Yes. Every calculator and span table on this site is free, with no sign-up. They run in your browser and use the same tables as our 3D deck designer.

The deck span, footing and stair limits come from the American Wood Council, Prescriptive Residential Wood Deck Construction Guide (DCA 6), 2015 edition, which is based on the 2015 International Residential Code. Pergola spans use the same engine as our pergola designer, with wood values from the National Design Specification. Paver and concrete figures come from the Interlocking Concrete Pavement Institute, the Portland Cement Association and the bag maker's published yields. Where a number is our own choice, the page says so.

They are planning figures. A permit office wants drawings of your own deck and may use a newer code or its own tables, so check with your building department. The builder's plan in our deck designer is drawn for that purpose.