Stud Layout for Cat Shelves: Every Stud from One Zero, the Bridge Span

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Opens on the book's own cat and wall. Change any number to your own and press Calculate.

Start from fills the boxes below

Lengths in

The wall

Wall width corner to corner

First stud's center from the left corner: your one zero

Stud spacing 16 in = 406.4 mm

Board past each bracket 1 in = 25.4 mm

The pieces, by stud number

Steps

Odd steps start on stud and the next

Even steps start on stud and the next

Lookout from stud

to stud

Post centered on stud 0 = none

Post width 4x4 = 88.9 mm

Enter the wall and press Calculate.

The formula

Stud n = first stud + (n − 1) × spacing, all from one zero at the left corner
Studs on the wall = (wall − first stud) ÷ spacing, rounded down, + 1
A board on studs a to b runs from stud a − the overhang to stud b + the overhang
Bridge span = the lookout's left end − the top step's right end. Brackets = 2 × steps + one per lookout stud

The book's worked example, Chapter 4. The first stud is 387.35 mm (15¼ in) from the left corner, so stud 9 is at 3,638.55 mm and 361.45 mm from the far corner. Odd steps sit on studs 1–2 (361.95 to 819.15 mm), even steps on studs 2–3 (to 1,225.55 mm), and the lookout on studs 6–8 (2,393.95 to 3,257.55 mm), so the bridge spans 1,168.4 mm (46 in). That is 15 brackets in all.

Find the first stud with a stud finder, then confirm it with a thin test hole where a board will cover it. Before you drill, check for cables and pipes: they often run straight up and down from outlets and switches. Metric first, imperial beside it. Prices are illustrative US home-center prices from November 2026, shown without a currency sign; put in your own. Everything stays in your browser: no sign-up, nothing stored.