Cat Landing Load: The Force on a Shelf and the Pull on Its Screws

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

Your cat's weight the heaviest cat

Weight in

Landing check × the weight; the book uses 6

The bracket as a lever

Landing point from the wall mm

Bracket heel to its top screw mm; 6 in = 152.4

The structural screw in the stud

Studs

Thread in the stud mm; 2 in = 50.8

Screws sharing the pull the top screw takes it

Two checks from the chapter (optional)

Drop height mm, for the soft-landing model

Stopping distance mm: legs and body giving

A plain wood screw

Its thread in the stud mm

Enter your cat and press Calculate.

The formula

Weight W = kg × 9.81. Landing load F = 6 × W (two front legs, up to about 3 × body weight each, from a 1 m jump-down)
Moment at the wall = F × the landing point's distance from the wall
Pull on the top screw = F × arm ÷ (heel to top screw): the bracket pivots on its foot
Margin = the screw's design hold ÷ the pull. A soft-landing model: F = W × (1 + drop ÷ stopping distance)

The book's worked example, Chapter 5. The design cat's 58.86 N × 6 = 353.16 N (79.39 lbf). Landing 250 mm from the wall on a bracket whose top screw is 152.4 mm above its heel, it pulls that screw with 579.33 N. A 5/16 in structural screw with 2 in of thread in an SPF stud has a design hold of 1,467.91 N, 2.53 times the pull. A 9 kg cat pulls 869 N: still 1.69 times.

Never hang a cat shelf on plastic wall plugs alone: at a quarter of its test load, the plastic anchor the book tested holds about 33 N. Fix every bracket into a stud. The 6 × check covers a cat jumping down from about 1 m; a heavier cat or a higher drop needs its own sum, and a professional if the margin is thin. 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.