I've heard humans stop growing around age 18-24. What about cats? When do they stop growing in height?
There are a couple of growth periods for cats. The first takes about 4 months and takes them into the kitten stage. The second growth period of a kitten takes them from about 4 months to somewhere between 8 and 12 months to adult size depending on the size of the breed. Larger breeds will take longer to reach their adult size versus smaller breeds, but despite having adult size, they're still junior cats, they don't really become adult cats until their 3rd year.
I only mention the two growth stages (which are effectively continuous) because the dietary requirements change.