My son is 5y/o and weights 45lbs. This shirt fits perfectly. The only reason it gets 4 stars is because the material isn't cottony as I had thought. It is more a stretchy, silky kind of fabric (more like a football jersey type of material). This could be advantageous as these types of fabrics don't burn out easily nor will they stretch out over time but, I'm still a bit disappointed as I prefer cotton shirts. Maybe I should have checked the product description.