Every website has recommended cage sizes. We can't recommend what size cage to buy. We don't know your needs. We don't know how much room you have. We don't know how much social time your bird experiences.
You may have many small birds you seek to house together. Our point? Choose the size cage that's right for you and your bird. Just make sure the bar spacing is appropriate.
Why is this so important? Birds are too smart for their own good. They're inquisitive. They like to know "what's going on." Basically we don't want them to get their heads caught in the bars.
Atthe same time, we had a male & female Indian Ringneck in an old cage with 1" bar spacing. He was fine for years. We had to clamp down the lift up food doors because she would try to lift them and escape. Moral of the story - there are no absolute rules when choosing a cage
It's also important to evaluate other areas of the cage where there is space say between the bottom of the front door and area below leading to the grate & the refuse tray. Some older cages have potentially problem gaps near the food dish doors. Please evaluate a new cage carefully.