How tall or long should a cat scratching post or scratcher be?

The ideal length of a cat scratching post or scratcher has mostly to do with how long your cat is. It should be tall enough or long enough for your cat to get a full stretch of the body. A vertical scratcher (e.g., freestanding scratching post) needs to accommodate nearly the full length of your cat (from back paws to outstretched front paws) while a horizontal scratcher (e.g., scratching pad that your cat stands on) can be shorter because of the different scratching angle (accommodating your cat's back and outstretched front paws).

Additionally, some scratchers allow your cat to sit or stand on the floor farther away from the scratcher which can compensate for the shorter length of the scratcher.

What sizes do scratching posts come in?

Kittens and smaller cats can make do with a smaller scratcher while a larger cat requires a taller or longer scratcher to get full stretch.

The scratching posts advertised for kittens can be around 20" while the ones for large cats can go up to around 40".

The taller the scratching post is the heavier and/or the wider the base needs to be to keep the post from wobbling too much or even tipping over when your cat uses it.

Not all cats use the post in the same way either. While some cats walk up to the post and gently start walking their paws higher as they scratch and stretch other cats attack the post by jumping at it from a running start. You just want to make sure your cat feels comfortable with the stability of the post.

If your cat attacks and climbs the post then it may be time to look for a cat tree or similar item that can not only be used for scratching but also climbing and perching.