Switching kid to a twin/full sized bed?

My son just turned 4 and he’s still in a toddler bed. He’s kind of small for his age, but I think he’s kind of outgrowing the toddler bed…. And he’s not a toddler anymore.

When did you guys go from the toddler bed to a twin or a full? Or did you skip the toddler bed altogether?

Also- Did you go with a twin size or a full size? He’s got a small room so a full size would take up more space obviously, but I feel like a twin is kind of small and he would outgrow that fast too.