BUY giant. Like from whatever size they are now, go like four sizes. Or two if they are not weeds(mine are).
My family(mil, mom, aunt and sisters)seem to think my kiddo's are grown. My oldest is in a size 7. he is very tall. So my MIL is buying 10-12 for him. Right now. I have corrected her eighty million times. She does not seem to hear me.
So I hang onto what she buys all of them....my oldest has the best luck, cause he normally can fit into what she buys for the younger two.
By the time he comes into fitting into to stuff, and he does not like some of the stuff, I take it up to my Consignment shop and we swap....They LOVE brand new stuff, and he gets to ''SHOP'' for his own stuff.
Buy big. You can never go wrong with a ''LITTLE TO BIG''.
FYI ON SNOW PANTS(someones comment made me think about this)....I FOUND SNOW PANTS AT THE END OF THE SEASON, FROM TARGET. THEY WERE ON CLEARANCE FOR 4 BUCKS....LIKE KID SIZE SNOW BOARD STYLE...NICE. JUST AN FYI THEIR WINTER CLEARANCE ROCKS.....I bought like four pairs....all next size up on for my oldest. We do not get snow here alot...but we can get cold for LONG periods of time....A deal worth sharing for this next year :)