True to size. My five-year-old is a size 6 (46” 47 lbs.) and this is a great fit. Light weight so it’s great for under a suit. A bit translucent though so if you’re thinking about this alone with dress pants, an undershirt or tank should be worn.

Size up due to slim fit. Worked well under a tuxedo for a wedding. The shirt that came with the tux rental was too uncomfortable for my toddler. Washed well and he wire it all night!