First of all, you should consider the amount of floor space you have available. Remember to take tree attachments, such as baskets, into your consideration.
Are There Any General Rules For The Size Of Cat Tree?
A cat tree should have a minimum height of around 36 inches. Since the average height of kitchen counter and sofa is 36 inches, this is the optimal height to discourage your cat from climbing on furniture.
Out in wild, cats climb the trees to hide or to prowl. Cats are territorial animals, and heights provide them to have a better look on their surroundings. Also, they spot their meal on the ground faster when they are somewhere high!