Deck and Stair Calculators

Plan a deck from the top down: how many boards and joists a deck needs, how much stain to buy, what a build adds up to with your own prices, how big the footings under it should be, and how to lay out stairs and stringers. Every calculator shows its steps and names the source of its figures; check local code and permit rules before you build.

Tools in this group

• Cost to Build a Deck Calculator — Enter the deck size and your own prices for boards, joists, labor and permit to get a total and a cost per square foot. No prices are built in.
• Deck Board Calculator — Enter the deck length and width, pick the board and its length, and get the number of boards to buy with waste, the board length in the deck and the joists at your spacing.
• Deck Board Dimensions — Pick a wood or composite board and a length to see its actual size and how much deck it covers, with the nominal and actual size chart below.
• Deck Footing Calculator — Enter the deck size, the post spacing and your soil bearing capacity to see how many footings you need and how big each one is, by the American Wood Council deck guide.
• Deck Joist Spacing Chart — Enter the deck length and joist length and a spacing to count joists, rim joists and blocking, then compare your spacing with the published maximums.
• Deck Ledger Board — Enter the joist span, the fastener and the house band joist to read the fastener spacing the AWC deck guide gives for a ledger, with the ledger size and fastener rules.
• Deck Railing Height — Enter how high your deck is above the ground to see when the code texts call for a guard, how tall it must be and how small the gaps must be, source by source.
• Deck Stain Calculator — Enter the deck area, the coats and the coverage on your can to get the gallons and cans of stain, with an optional cost from your own price.
• Deck Stair Calculator — Enter the deck height and the riser height or tread depth you want to get the risers, treads, run, stringer length and angle, with a side-view drawing.
• Sonotube Sizes — Pick a round form size and the concrete height to see the volume in one tube, with the maker chart beside the geometry and the smallest tube for your footing diameter.
• Stair Stringer Calculator — Enter the rise, tread depth and stair width to get the stringer length, the throat left in a 2x12, how many stringers to cut and where to mark the board.