What's the difference between 24 months and 2T? Does it vary by brand? I need to get C some fleece pjs and I like the target Carter's ones but they go straight from 18m to 2t. Wondering if they will be way too big.

I thought they were similar size but 24 m are shorter and wider while 2t are longer and narrower. C is kind of short and chubby. 18m fit now but since I'm buying for winter want to go up a size.