Calvert-Lewin has been one of the Premier League's standout players in 2020/21, scoring 11 goals in 14 appearances so far. Only Mohamed Salah has scored more so far this campaign.
He is now a regular in the England squad, too, and Ancelotti believes his physicality is what is making him stand apart at the moment.
“He is a special player,” the 31-year-old told talkSPORT.
“He has fantastic abilities.
“Game-by-game you can see his improvement and how he is able to make the difference in this league. It’s not easy to make the difference.
“Especially from a physical point of view, it’s difficult to see a player in this league that is better than the others because the level is really high.
“But Dominic is able to impress from this point of view.”
It is Calvert-Lewin's physicality that led Ancelotti to compare him to Ronaldo, whom the Italian coach worked with at Real Madrid under his dad Carlo.
“The special ability he has, that all the big talents have, is that he knows his body really well," Ancelotti explained.
"He knows his feelings really well and that’s not so common.
“For example, [Cristiano] Ronaldo was a player like this. He was able to understand his body.”