Obviously, some of it depends on genetics and your family, but most babies I've seen including ds have drastically slowed down in their growth around the one year mark. It may have something to do with them starting to learn verbal and other skills at this point. I'd probably buy the 18 month size. My ds is 19 months and is in the 24 month sizes. He still fit into his 18 month sizes until a couple of months ago. I don't think you could go wrong buying the 24 month tops, but I'd probably insist on having bottoms closer to size just so they aren't a hindrance and dragging the ground when he's walking. Sleeves can always be rolled up.

This is my opinion only. I realize that others have differing opinions. I hate to see kids wearing clothes that do not fit them well. They always look like slobs.

I have a friend that buys her son's clothes 2 sizes to big and they are always rolled up at the bottom, rolled up at the sleeves, and hanging down to his knees. She buys him expensive clothes but he never looks nice because by the time they fit him right they are all worn out and old looking from being washed so often.

I buy my kids clothes that fit them right or are slightly big on them. When they outgrow them I buy them new clothes. I have 3 kids so the younger ones wear the hand me downs when they are ready for them.

If he is just outgrowing the 12 month size now I would buy him 18 months size next. Remember they do not grow as fast the second year as they did the first year. That's normal.

Mommabear

I agree, unless this little guy is big for his age, I would buy him 18mos....especially if you are going with an outfit, pre made/presized.
Now on the other hand- if you pick and chose pieces/coordinates and put it together yourself, which is what I always like to do, then I would say get the shirt in a 24mos and the pants in 18mos... My son wears bigger tops than bottoms! It is REALLY important to buy pants that will at least CLOSE To fit, otherwise it's a danger for a running, walking, toddling toddler!! Pants can be rolled up, but it never looks good and sometimes the waists are too large, which is an even worse problem!

If I buy outfits for my 17mos old son, size 24mos, he won't be able to wear the pants for many months-since he wears 12/18mos bottoms! Personally I would try to avoid buying an "outfit" and piece a great outfit together yourself, catering each piece of clothing to the child...you can gage each item on looks...some size 12mos run the same as a 18mos, even a size 2t can look like a 5t!! Your eye is sometimes your best judge!

Worst case scenario, your friend can return the item if it doesn't fit!

Keeping in mind, like the other posters said, growth slows down A LOT after they hit the 12mos size mark..my son is now almost 18mos...wearing clothes from 12mos-24mos, even many 2 and 3t tops..yet 18mos pants and he is average size!

~Happy Shopping!
~JEN.

I vote 18 months.

I many times would buy a larger top then bottom, meaning in your case a 24mo. size top and and 18 mon. size bottom. The one size large top that I bought never did look bad. bad.

Now it would look bad to buy the larger size IF the sleeves on the top were way too long and the top was way to large all over. Many times the tops are not. It would be all according to how the top fit. But if you can get a larger top-and it looks good-then later you could still use it possibly with a 24mo. bottom, later.
I would hold up the 18mo. top and compare to see if it indeed was that much smaller than the 24mp. top.

At any rate I would buy the 18mo. bottoms where the child could walk properly in the pants and also not have the pants falling down from his waist. Possibly the 18mo. top would not fit too snuggly(have a little growing room to it). It all depends on how the top is made!
~Lynn~

I try to go by the weight rather than the ages. Different brands use different weights/lengths for each size. If you know his weight, I'd try to buy him something that would fit now, but that he'd be in the lower end of the range. I.e. if he weighs 22 lbs, find the size that fits something like 21-26 lbs, rather than a size where he's on the high end and will soon outgrow it. If he's a big baby, and/or the brand runs small, that might mean buying a 24 mo. size now. However if he's close to 1 year and just now growing out of his 12 mos. clothes, I'll bet the 18 mo. size will be the right choice for you.

I also vote 18 months...my son was 2 in sept. and wears 24m (and he is tall for his age).