Does my baby Weights more than normal? 17 weeks pregnant and is a boy.?

My baby weights about 7.8 ounces (221 grams) and is 5.9 inches long (15cm). He's 17 weeks old according to the doctors calculations and we know is around 16 weeks. But I have been looking online and he's like a 19 week baby. The person doing the sonogram said he was good. What you guys know or think about the weight and the Length?