Calculators
Shopping lists, not span tables
Four small tools for a rectangular deck. Each one shows the arithmetic. None of them says a footing, a joist, or a rail will pass an inspection.
Last updated October 25, 2026
Boards, screws, joists
Deck board calculator
Rows, stock lengths, a screw estimate, a simple joist count, and a price you can edit. Opens on a 12×16.
Finish
Stain and sealer coverage
Square feet, coats, and the coverage printed on the can. Stairs and rails are extra.
Concrete
Footing bags
Round tube volume divided by the cubic feet printed on the bag.
Guard
Railing balusters
How many balusters keep the opening at or under the gap you type. Check that gap locally.
Which one to open first
Start with the board calculator if you are buying decking. The count depends on which way the boards run, the real face width, and the gap. A 12×16 is not one number.
Open stain after the deck is built, or when you are pricing a refinish of a deck you already have. Coverage is area times coats, divided by the square feet per gallon on the label.
Open footings only for round cardboard tubes. It does not size a footing, pick a depth below frost, or design a bell. It converts a cylinder into bags.
Open balusters when the posts are already spaced, or when you want a shopping count for a straight run or a closed pen. A 4 inch opening is a common guard rule of thumb. Your inspector can require something else.
The guides walk through the same math with worked sizes.